What is the meaning of intravascular volume?
In medicine, intravascular volume status refers to the volume of blood in a patient's circulatory system, and is essentially the blood plasma component of the overall volume status of the body, which otherwise includes both intracellular fluid and extracellular fluid. Still, the intravascular component is usually of primary interest, ...
What is the meaning of interstitial space?
Related to intravascular space: interstitial space in·tra·vas·cu·lar (ĭn′trə-văs′kyə-lər) adj. Within blood vessels or a blood vessel. in′tra·vas′cu·lar·lyadv.
How much water is in the intracellular space?
Total body water = intracellular space + intravascular space + interstitial space. In a 70kg adult, the intracellular space holds approximately 23 litres of fluid in comparison to 17 litres in the extracellular space, where 5 litres of blood volume is in the intravascular space (Amato, et al.
What is the extracellular space?
The rest is found in what is referred to as the extracellular space, which consists of the blood vessels ( intravascular space) and the spaces between cells (interstitial space). * Avoid direct injection into the intravascular space.
What is the function of the endothelium?
What is the BBB between the brain and the capillary?
How do leukocytes migrate to extravascular sites?
What are the three types of selectins?
What are integrins in the cell?
How do leukocytes migrate to the lungs?
What is the most abundant protein in the intravascular space?
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What makes up the intravascular space?
Intravascular Compartment The main intravascular fluid in mammals is blood, a complex fluid with elements of a suspension (blood cells), colloid (globulins) and solutes (glucose and ions). The average volume of plasma in the average (70 kg) male is approximately 3.5 liters.
What is intravascular and extravascular space?
The intravascular compartment contains fluid (i.e., blood) within the cardiac chambers and vascular system of the body. The extravascular system is everything outside of the intravascular compartment. Fluid and electrolytes readily move between these two compartments.
What is the intravascular fluid space?
The main intravascular fluid in mammals is blood, a complex mixture with elements of a suspension (blood cells), colloid (globulins), and solutes (glucose and ions). The blood represents both the intracellular compartment (the fluid inside the blood cells) and the extracellular compartment (the blood plasma).
What causes fluid to stay in the intravascular space?
Oncotic versus Hydrostatic Pressure The oncotic pressure keeps fluid in the intravascular space by either holding on to it or pulling it from the interstitial or intracellular spaces. The oncotic pressure is predominantly influenced by the large proteins, such as albumin, found within the intravascular space.
What are the 3 fluid spaces?
There are three major fluid compartments; intravascular, interstitial, and intracellular. Fluid movement from the intravascular to interstitial and intracellular compartments occurs in the capillaries.
Is the intravascular space ECF?
The main component of the extracellular fluid (ECF) is the interstitial fluid, or tissue fluid, which surrounds the cells in the body. The other major component of the ECF is the intravascular fluid of the circulatory system called blood plasma. The remaining small percentage of ECF includes the transcellular fluid.
Where is the intravascular fluid located?
The first type is known as intravascular fluid that is found in the vascular system that consists of arteries, veins, and capillary networks. Intravascular fluid is whole blood volume and also includes red blood cells, white blood cells, plasma, and platelets.
Where is the extravascular space?
The space that surrounds the cells of a given tissue, which is filled with interstitial fluid which bathes and surrounds cells.
Is intravascular the same as extracellular?
Interstitial fluid, intravascular fluid, and transcellular fluid are three types of extracellular fluid compartments. The interstitial fluid compartment sometimes is called tissue space.
What is the difference between intravascular and interstitial?
Gases such as oxygen and carbon dioxide diffuse freely through this membrane, following their concentration gradient, to enter or exit the intravascular compartment. The interstitial compartment is the space between the capillaries and the cells. Fluids support the matrix and cells within the interstitial space.
What causes intravascular dehydration?
True volume depletion may occur when sodium-containing fluids are lost in the urine, from the gastrointestinal tract or skin, or by acute sequestration into an internal "third-space" that results in a diminished intravascular volume.
What IV fluids increase intravascular?
Crystalloid fluids function to expand intravascular volume without disturbing ion concentration or causing significant fluid shifts between intracellular, intravascular, and interstitial spaces. Hypertonic solutions such as 3% saline solutions contain higher concentrations of solutes than those found in human serum.
What is the difference between intravascular and extravascular hemolysis?
Intravascular hemolysis occurs when erythrocytes are destroyed in the blood vessel itself, whereas extravascular hemolysis occurs in the hepatic and splenic macrophages within the reticuloendothelial system.
What are the 2 fluid compartments?
The body's fluid separates into two main compartments: Intracellular fluid volume (ICFV) and extracellular fluid volume (ECFV).
What is intravascular and interstitial?
Gases such as oxygen and carbon dioxide diffuse freely through this membrane, following their concentration gradient, to enter or exit the intravascular compartment. The interstitial compartment is the space between the capillaries and the cells. Fluids support the matrix and cells within the interstitial space.
What are the 2 fluid compartments differentiate them?
Total body water can be subdivided into two major compartments, intracellular fluid which is fluid inside cells, and extracellular fluid which is fluid outside of cell like in the blood and in the interstitial tissue between cells.
Intravascular space | definition of intravascular space by Medical ...
Extravascular Less severe, IgG-mediated and does not activate complement, eg Rh, Kell, Duffy Laboratory ↓ haptoglobin, ↓ T 1/2 of circulating RBCs, ↑ indirect BR as liver capacity to conjugate BR–ergo direct BR is overwhelmed by massive hemolysis, ↑ LDH, Hb in blood and urine, hemosiderinuria, MetHb and metalbumin, ↑ urobilinogen in urine and feces, ↑ in acid phosphatase, K+, and ...
Attic / Intersitial Space | The Building Code Forum
Wondering if anyone would happen to know where specifically the IBC defines interstitial space, or if an attic would be considered a specific type of inerstitial space? Thanks in advance!
Interstitial Space Design in Modern Laboratories | Journal of ...
Associate Professor, Dept. of Architectural Engineering, Penn State Univ., 104 Engineering Unit A, University Park, PA 16802.
Interstitial spaces | definition of Interstitial spaces by Medical ...
Interstitial spaces: Spaces within body tissues that are outside the blood vessels. Interstitial spaces are also known as interstitial compartments. Mentioned in: Edema , Electrolyte Supplements
How much fluid does a 70kg human hold?
In a 70kg adult, the intracellular space holds approximately 23 litres of fluid in comparison to 17 litres in the extracellular space, where 5 litres of blood volume is in the intravascular space (Amato, et al., 2008).
What causes water to move from the interstitial to the intravascular space?
The accumulation of osmotically active substances such as glucose and lipids may also dilute sodium levels by causing water to move from the interstitial to the intravascular space. Symptoms of hyponatremia are the result primarily of CNS water intoxication and brain swelling (Kokko, 2000; McSweeney, 2000).
What should a nurse assess for fluid overload?
The nurse should assess often for fluid volume overload in patients receiving hypertonic solutions as the fluid moves out of the cells and into the intravascular space. Assessment findings such as auscultated rales or crackles in the lung fields, shortness of breath, dyspnea, and jugular vein distention might indicate the patient is developing fluid volume overload.
What is the role of dextran in vascular physiology?
The dextran component binds the recruited water within the intravascular space, thus sustaining the volume expansion achieved and stabilising haemodynamics.
What is the term for the presence of Hb in urine?
Hematology The presence of Hb in the urine which, if of sufficient quantity, colors urine, the intensity of which directly correlates with the quantity of Hb. See Paroxysmal cold hemoglobinuria, Paroxysmal nocturnal hemoglobinuria.
Does mannitol increase blood flow?
Mannitol acts as an immediate plasma expander by drawing fluid from extravascular to intravascular space, as a result improving cerebral blood flow which in turn causes cerebral vasoconstriction.
Do serum electrolytes represent total body depletion?
Serum electrolytes only represent values within the intravascular space and do not represent total body depletion.
Why are colloids better than crystalloids?
Colloid advocates claim that, because these solutions have an intravascular space half-life of 3 to 6 hours (much greater than crystalloids), they are superior resuscitation fluids. When compared to crystalloids in a controlled fashion, they have not been shown to improve outcomes. Further, in cases in which capillary permeability increases (e.g., burns, sepsis, trauma), colloids accumulate extracellularly, pulling other fluids along because of the osmotic gradient, resulting in extracellular edema. Finally, colloid solutions are more expensive.
What is the BBB between the brain and the capillary?
The BBB between the capillary intravascular space and the brain parenchymal interstitial space is composed of capillary endothelial cells bound together by tight junctions and closely packed astrocytic podocytes (Bellavance et al., 2008 ). The lipid bilayers of the endothelium are the primary barrier, thus helping to explain why lipophilic compounds are generally better at crossing the BBB than nonlipophilic compounds ( Begley, 1996 ). In addition to the transcellular lipophilic pathway, the BBB can be penetrated via a paracellular aqueous pathway (aqueous compounds through tight junctions), specific cell-surface protein receptors (e.g., glucose, amino acids, peptides, vinca alkaloids, cyclosporine A, AZT), receptor-mediated transcytosis (e.g., insulin and transferrin), and adsorptive transcytosis (e.g., albumin and other plasma proteins) ( Abbott et al., 2006 ). In particular, the paracellular tight junction pathway can be osmotically permeabilized with IA administration of hypertonic mannitol just before IA or IV administration of a chemotherapy drug; this remains the most common BBB disruption strategy despite induction of significant nausea in patients ( Muldoon et al., 2007; Chakraborty et al., 2016 ). Initially developed as a high-power ablative technology ( Chen et al., 2010; McDannold et al., 2010 ), MRI-guided high-intensity focused ultrasound (MRgFUS) has more recently emerged as a sublative method for transiently permeabilizing the BBB in a spatially specific manner prior to drug administration ( Kinoshita et al., 2006; Treat et al., 2007; Deckers et al., 2008; Nance et al., 2014 ). Pioneering work is also being done on using MRgFUS to modulate gene expression within normal tissues and within tumors themselves ( Deckers et al., 2009 ).
How does fluid leave the capillary?
Fluid leaves the intravascular space as blood is forced through the capillary bed. This fluid bathes the cells and is picked up by the lymphatic system and delivered back into the bloodstream in the common thoracic duct. The capillary wall is the barrier between these two compartments, and the movement of fluid across this barrier is described by the relationship formulated by the physiologist Starling. This situation is different from the movement of water across the cell membrane. In a capillary, water and dissolved solutes move equally well across the capillary wall. The solutes do not generate any osmotic pressure because they flow with the water across the barrier. However, the plasma proteins (particularly albumin) do not move readily across the capillary wall. The plasma proteins, unlike the dissolved solutes, exert a force called oncotic pressure that retards the net movement of fluid out of the capillary.
What is the difference between a capillary and a tissue hydrostatic pressure?
Thus the net difference between capillary and tissue hydrostatic pressure (P c − P t) is the driving force promoting filtration or absorption of fluid out of or into the capillary lumen.
How long does 99m Tc last?
Because the technetium red blood cell bond lasts considerably longer than does the 6-hour half-life of 99m Tc, the physical half-life of the radiopharmaceutical determines the length of time over which serial imaging is possible. With the use of 20 to 30 mCi (740 MBq to 1.11 GBq) of 99m Tc-pertechnetate, delayed imaging is possible for up to 10 to 12 hours after injection.
What are the three types of selectins?
The selectin family includes L-selectin, P-selectin, and E-selectin. L-selectin is expressed on the surface of PMNs and is shed shortly after activation in vitro. 714 P-selectin is stored in endothelial cells and rapidly mobilized to the surface after initial endothelial activation. 715 E-selectin (endothelial-leukocyte adhesion molecule) is expressed on the surface of endothelial cells only after activation by bacterial products or mediators including C1q, TNF-α, IL-1β, and IL-10. 716,717 PMN receptors for the endothelial selectins include PSGL-1 and sialyl Lewis X antigen (sLe x ), an oligosaccharide present on many proteins including the PMN adhesins L-selectin and CD11/CD18. 718
What are integrins in the cell?
The integrins are a family of proteins involved in cell adhesion and motility. Present on leukocyte membranes, these molecules adhere to specific endothelial ligands and various components of connective tissue matrix. The integrins are expressed as heterodimers, each containing one α and one β chain; subclassification of these adhesins is based on specific α/β chain content. 701,702 The α4 integrins are expressed at high levels on monocytes, lymphocytes, and eosinophils. Although typically absent from neutrophils, α4 integrin is present on immature PMNs, or on mature forms under conditions of transendothelial migration or chemokine stimulation. 703,704 The β1 integrins include VLA-4, found on lymphocytes and monocytes. 705 The β2 integrins include CD11a/CD18, constitutively expressed on all leukocyte subsets, and CD11b/CD18 and CD11c/CD18, which are prominent adhesins of PMNs. 706 Because the PMN must deform to navigate the narrow alveolar capillary space, the PMN surface membranes are brought into close contact with those of the vascular endothelium, inviting adherence interactions. 707 CD11/CD18 is therefore maintained in an inactive state, until chemotactic activation occurs. 708 PMN activation results in a CD11/CD18 conformational change to an activated form that recognizes its corresponding endothelial ligand. 709 PMN activation also results in mobilization of a significant intracellular stored pool of CD11/CD18, facilitating additional rapid surface expression of this molecule, 706 although the constitutively smaller pool in neonatal PMNs may tend to blunt this response.
How does colloid help the intravascular space?
The increase in plasma oncotic pressure produced by colloid helps draw fluid into the intravascular space and thereby expands the plasma volume and remains in the intravascular space for a long time.
What is the most common type of cerebral edema?
Vasogenic edema, the most common type of cerebral edema, is secondary to the movement of albumin, other plasma proteins, and fluid from the intravascular space into the extravascular space.
What is hypertonic IV?
Hypertonic IV solutions are fluids with solutes greater than 0.9%, such as 3.0% NS, [D.sub.5] NS, and [D.sub.5]LR, which pull fluid from cells into the intravascular space. Hypertonic solutions are useful for patients with elevated intracranial pressure (ICP) and some trauma patients (Patanwala et al., 2010; Phillips et al., 2009).
What antigens are most commonly expressed in B cells?
Microscopy will demonstrate large B cells sequestered within the intravascular spaces; these cells inconsistently express several of the typical B-cell antigens, with CD79a, CD20, MUM1/ IRF4, and CD19 being the most commonly expressed.
What is the osmotically active particle in the muscle?
Osmotically active particles (e.g., lactate) in the active muscles draw an influx of fluid from the intravascular space into the interstitial and intramuscular spaces (20,21,25).
Does type 1 diabetes increase transcapillary escape rates?
Danish investigators have demonstrated that type 1 diabetic patients have increased transcapillary escape rates of LDL cholesterol from the intravascular space into the arterial wall (Atherosclerosis 2003;170:163-8).
Where is the rest of the body found?
The rest is found in what is referred to as the extracellular space, which consists of the blood vessels ( intravascular space) and the spaces between cells (interstitial space).
What is OHSS in ovulation?
To the Editor: Ovarian hyperstimulation syndrome (OHSS) is an iatrogenic complication of ovulation induction, with ovarian enlargement and acute fluid shift from the intravascular space. The incidence of severe OHSS is approximately 1-2% of treatment cycles and usually following in vitro fertilization embryo transfer (IVF-ET) treatment.
What is the most common type of cerebral edema?
Vasogenic edema is the most common type of cerebral edema and develops as a result of breakdown of blood brain barrier and consequent albumin and fluid shift from the intravascular spaceand into the extravascular space.
What is the mechanism of sequestration of IVLBCL?
Alternate theories of the mechanism of sequestration of IVLBCL to the intravascular spaceinclude deficient expression of receptors for peanut agglutinin and CD49d, both of which promote homing of tumor cells to endothelial cells via interaction with CD54 and CD106 (CD49d ligand).
What is the result of greater regional pressure?
This greater regional pressure results in a concomitant filtration from the regional intravascular spaceto the interstitial space (14,16) , which results in an increase in both Hct (12) and Hb (21).
What equipment gets stuck in the intravascular space?
Several types of equipment, including guidewire, vascular sheath, or suboptimally uncoiled stents may get stuck in the intravascular space, causing complications (8).
What is TURP syndrome?
TURP syndrome involve s more rapid direct extravasation of fluid into the intravascular space. The full metabolic effects of intraperitoneal fluid absorption due to bladder perforation are therefore delayed.
Is hydroxyethyl starch hyperoncotic?
Hydroxyethyl starch being hyperoncotic, has the ability to withdraw fluid from interstitial into intravascular space. Extent of volume expansion is 150%.
What causes extrarenal volume depletion?
Extrarenal causes include bleeding, burns, and any causes of edema (e.g. congestive heart failure, liver failure). Intravascular volume depletion is divided into three types based on the blood sodium level: Isonatremic (normal blood sodium levels) Example: a child with diarrhea, because both water and sodium are lost in diarrhea.
What is intravascular volume?
Jump to navigation Jump to search. In medicine, intravascular volume status refers to the volume of blood in a patient's circulatory system, and is essentially the blood plasma component of the overall volume status of the body , which otherwise includes both intracellular fluid and extracellular fluid.
Why is the intravascular volume of water low?
Overall there is more water than sodium in the body. The intravascular volume is low because the water will move through a process called osmosis out of the vasculature into the cells (intracellularly). The danger is tissue swelling (edema) the most important being brain edema which in turn will cause more vomiting.
What is a BVA 100?
For the clinical assessment of intravascular blood volume, the BVA-100, a semi-automated blood volume analyzer device that has FDA approval, determines the status of a patient’s blood volume based on the Ideal Height and Weight Method. Using a patient’s ideal weight and actual weight, the percent deviation from the desirable weight is found using the following equation:
What is the contraction of blood plasma called?
Volume contraction of intravascular fluid ( blood plasma) is termed hypovolemia, and its signs include, in order of severity: a fast pulse.
What causes hypovolemia in the kidney?
The most common cause of hypovolemia is diarrhea or vomiting. The other causes are usually divided into renal and extrarenal causes. Renal causes include overuse of diuretics, or trauma or disease of the kidney. Extrarenal causes include bleeding, burns, and any causes of edema (e.g. congestive heart failure, liver failure).
Is intravascular volume depletion the same as intravascular volume depletion?
Still, the intravascular component is usually of primary interest, and volume status is sometimes used synonymously with intravascular volume status . It is related to the patient's state of hydration, but is not identical to it. For instance, intravascular volume depletion can exist in an adequately hydrated person if there is loss ...
What is the function of the endothelium?
As an anatomic boundary between the intra- and extravascular spaces, the endothelium acts as a selective permeability barrier to regulate the transport of water, solutes, and macromolecules through the synthesis and maintenance of specialized intercellular junctions, as well as via transcellular pathways involving vesicles, channels, and transporters. 30 The selectivity of the endothelial barrier function varies throughout the vasculature and this regional specialization is dependent on the endothelial structure, as well as the characteristics (i.e., size, charge, metabolic processing needs) of the solute to be transported.
What is the BBB between the brain and the capillary?
The BBB between the capillary intravascular space and the brain parenchymal interstitial space is composed of capillary endothelial cells bound together by tight junctions and closely packed astrocytic podocytes (Bellavance et al., 2008 ). The lipid bilayers of the endothelium are the primary barrier, thus helping to explain why lipophilic compounds are generally better at crossing the BBB than nonlipophilic compounds ( Begley, 1996 ). In addition to the transcellular lipophilic pathway, the BBB can be penetrated via a paracellular aqueous pathway (aqueous compounds through tight junctions), specific cell-surface protein receptors (e.g., glucose, amino acids, peptides, vinca alkaloids, cyclosporine A, AZT), receptor-mediated transcytosis (e.g., insulin and transferrin), and adsorptive transcytosis (e.g., albumin and other plasma proteins) ( Abbott et al., 2006 ). In particular, the paracellular tight junction pathway can be osmotically permeabilized with IA administration of hypertonic mannitol just before IA or IV administration of a chemotherapy drug; this remains the most common BBB disruption strategy despite induction of significant nausea in patients ( Muldoon et al., 2007; Chakraborty et al., 2016 ). Initially developed as a high-power ablative technology ( Chen et al., 2010; McDannold et al., 2010 ), MRI-guided high-intensity focused ultrasound (MRgFUS) has more recently emerged as a sublative method for transiently permeabilizing the BBB in a spatially specific manner prior to drug administration ( Kinoshita et al., 2006; Treat et al., 2007; Deckers et al., 2008; Nance et al., 2014 ). Pioneering work is also being done on using MRgFUS to modulate gene expression within normal tissues and within tumors themselves ( Deckers et al., 2009 ).
How do leukocytes migrate to extravascular sites?
The initial step in leukocyte migration to extravascular sites is a slowing of leukocyte movement through the area of inflammation by a series of loose, transient, leukocyte-endothelial cell adhesions, characterized as “roll ing.” This step is mediated through interaction of endothelial selectins with PSGL-1 and L-selectin on the PMN surface. 719 Low L-selectin and sLe x concentrations on neonatal PMN surfaces have been implicated in impaired chemotaxis but are likely not relevant in the pulmonary circulation, where the constrained vascular space obviates the need for this receptor-ligand interaction. 720 The next step entails binding of local chemotactic activators (C3a, C5a, IL-8, PAF) to the rolling PMN, inducing expression and activation of CD11/CD18 and shedding of L-selectin. 719 Subsequently, the leukocytes firmly attach to the endothelium via a CD11/CD18 to ICAM-1 interaction (PMNs) or by means of a VLA-4 to VCAM-1 interaction (mononuclear cells, lymphocytes). 721,722 The final step is diapedesis of the adherent leukocyte through the vessel wall and migration along a chemotactic gradient to the site of inflammation. Although this process remains incompletely characterized, transendothelial migration appears mediated by the adhesion molecules PECAM and the integrin-associated protein CD47. 723 Once extravasated, neutrophils appear to follow a fixed chemotactic gradient laid down in the extracellular matrix, migrating along interstitial fibroblasts and eventually squeezing between type I and type II epithelial cells to reach the air spaces of the lung. 724
What are the three types of selectins?
The selectin family includes L-selectin, P-selectin, and E-selectin. L-selectin is expressed on the surface of PMNs and is shed shortly after activation in vitro. 714 P-selectin is stored in endothelial cells and rapidly mobilized to the surface after initial endothelial activation. 715 E-selectin (endothelial-leukocyte adhesion molecule) is expressed on the surface of endothelial cells only after activation by bacterial products or mediators including C1q, TNF-α, IL-1β, and IL-10. 716,717 PMN receptors for the endothelial selectins include PSGL-1 and sialyl Lewis X antigen (sLe x ), an oligosaccharide present on many proteins including the PMN adhesins L-selectin and CD11/CD18. 718
What are integrins in the cell?
The integrins are a family of proteins involved in cell adhesion and motility. Present on leukocyte membranes, these molecules adhere to specific endothelial ligands and various components of connective tissue matrix. The integrins are expressed as heterodimers, each containing one α and one β chain; subclassification of these adhesins is based on specific α/β chain content. 701,702 The α4 integrins are expressed at high levels on monocytes, lymphocytes, and eosinophils. Although typically absent from neutrophils, α4 integrin is present on immature PMNs, or on mature forms under conditions of transendothelial migration or chemokine stimulation. 703,704 The β1 integrins include VLA-4, found on lymphocytes and monocytes. 705 The β2 integrins include CD11a/CD18, constitutively expressed on all leukocyte subsets, and CD11b/CD18 and CD11c/CD18, which are prominent adhesins of PMNs. 706 Because the PMN must deform to navigate the narrow alveolar capillary space, the PMN surface membranes are brought into close contact with those of the vascular endothelium, inviting adherence interactions. 707 CD11/CD18 is therefore maintained in an inactive state, until chemotactic activation occurs. 708 PMN activation results in a CD11/CD18 conformational change to an activated form that recognizes its corresponding endothelial ligand. 709 PMN activation also results in mobilization of a significant intracellular stored pool of CD11/CD18, facilitating additional rapid surface expression of this molecule, 706 although the constitutively smaller pool in neonatal PMNs may tend to blunt this response.
How do leukocytes migrate to the lungs?
Leukocyte migration from the intravascular space to an eventual inflammatory locus within the lung is a multistep process, dependent on mechanisms directing cell movement to the appropriate site ; leukocytes must marginate and adhere to the vascular endothelium, followed by diapedesis between endothelial cells and movement from the vascular space.699,700 Directed movement along concentration gradients of chemotaxins is one mechanism, while another is haptotaxis, or directed migration along gradients of endothelial adhesiveness. This latter process requires the presence of both leukocyte- and endothelial-derived adhesion molecules and is mediated by three families of molecules: the integrins, the immunoglobulin gene superfamily, and the selectins.
What is the most abundant protein in the intravascular space?
HSA is the most abundant protein in the intravascular space (∼0.6 mM), constituting 60% of total plasma protein, and is also present extravascularly in extracellular tissue compartments. It contains only one free cysteine, Cys34 (HSA-SH), which is the main plasma thiol, representing > 80% of free thiols in the circulation ( Peters, 1996 ). It has been proposed to participate in the scavenging of oxidant species, mostly due to the presence of the Cys34 thiol. Indeed, HSA-SH is able to react with different oxidants, including peroxynitrite and its derived radicals. The reaction with peroxynitrite occurs with a second order rate constant of 3.8 × 10 3 M −1 s −1 ( Alvarez et al., 1999 ). This reactivity is comparable to that of low molecular weight thiols such as free cysteine (k = 5.9 × 10 3 M −1 s −1; Radi et al., 1991b) and glutathione (k = 1.35 × 10 3 M −1 s −1; Koppenol et al., 1992 ), and is consistent with the apparent pK a value of the albumin thiol of 8.3–8.6 ( Alvarez et al., 1999 ), as illustrated in Fig. 2. The reaction with two-electron oxidants leads to a relatively stable sulfenic acid (HSA-SOH) ( Carballal et al., 2003 ), which can react with a thiol such as cysteine leading to a mixed disulfide (HSA-SSR) or be further oxidized to sulfinic (HSA-SO 2 H) and sulfonic (HSA-SO 3 H) acid. No evidence has been obtained for the formation of sulfenamides or intermolecular disulfide dimers. A recent analysis of the reactivity of albumin sulfenic acid ( Turell et al., 2008) supports quantitatively a role for this intermediate in the formation of mixed disulfides and higher oxidation states, which can be observed in ∼25% of circulating albumin.
