Serum albumin, half-life

Short-Term Monitors. These include labile pre-Hb Aj (several days), glycosylated serum transferrin, half-life of 8 days (K3, K4) and glycosylated serum albumin, half-life of 20 days (D23, J6). These estimations... 

Absorption kinetic studies on fasted rats dosed by lipid-emulsion gavage revealed rapid appearance of triehloroethylene in the blood (typieally peaking at 15 minutes post-exposure) followed by rapid disappearance (Templin et al. 1993). Rats similarly dosed with radiolabelled trichloroethylene showed rapid serum albumin adduction which peaked at 4-8 hours, then decayed with a half-life consistent with that of albumin itself (Stevens et al. 1992). However, some of the detected radioactivity may have been due to trichloroethylene metabolites rather than the parent compound. 

There is substantial variability in the pharmacokinetics of vinblastine in patients. Evidence has been obtained that implicates altered liver function and dose-dependent elimination as contributing factors to the variable pharmacokinetics. When vinblastine was administered by a bolus injection, a mean terminal elimination half-life of 29.2 hr was estimated for a group of 24 patients, but the half-lives ranged from a low value of 16 hr to a high value of 65 hr (55). When vinblastine was administered by intravenous infusion, clearance of the drug appeared to decrease with time over a 4-month period decreases in serum albumin values were found to be correlated with decreases in the clearance of vinblastine. 

Serum alkaline phosphatase elevations have been reported following administration of salt-poor albumin (B5). Placenta is very rich in a heat-stable alkaline phosphatase, and albumin prepared from placental blood has a high activity of this enzyme. In one cirrhotic patient who received 1-6 units per day of albumin obtained from pooled human blood and/or human placenta, the alkaline phosphatase before infusion was 5 Bodansky units and by the thirteenth day of administration had reached a value of 160 units. The physician administering the albumin at first thought the patient was having a severe toxic liver reaction and stopped the therapy. The alkaline phosphatase then started to go down and within 10 days returned to normal levels. Analysis of the albumin indicated that it contained 470 units of alkaline phosphatase activity and was probably responsible for the observed elevations in the serum enzyme activity. Albumin prepared from venous blood did not cause an alkaline phosphatase elevation, but placenta-albumin caused elevations with a half-life of about 8 days (Ml). 

Pharmacokinetics Absorption varies. Food increases peak serum levels. Reversibly bound to albumin. Metabolized in the liver. Excreted in the urine. Half-life 2 hr... 

Diazoxide is similar chemically to the thiazide diuretics but has no diuretic activity. It is bound extensively to serum albumin and to vascular tissue. Diazoxide is partially metabolized its metabolic pathways are not well characterized. The remainder is excreted unchanged. Its half-life is approximately 24 hours, but the relationship between blood concentration and hypotensive action is not well established. The blood pressure-lowering effect after a rapid injection is established within 5 minutes and lasts for 4-12 hours. 

Salicylic acid is a simple organic acid with a pKa of 3.0. Aspirin (acetylsalicylic acid ASA) has a pKa of 3.5 (see Table 1-3). The salicylates are rapidly absorbed from the stomach and upper small intestine yielding a peak plasma salicylate level within 1-2 hours. Aspirin is absorbed as such and is rapidly hydrolyzed (serum half-life 15 minutes) to acetic acid and salicylate by esterases in tissue and blood (Figure 36-3). Salicylate is nonlinearly bound to albumin. Alkalinization of the urine increases the rate of excretion of free salicylate and its water-soluble conjugates. 

Tags comprise sequences that go from a few amino acids (His-, FLAG-or c-myc-tags) to large polypeptides (serum albumin, protein A or G, glutathione S-transferase, growth hormone, GFP, CAT, etc.). The purpose of a tag is to confer a novel property such as an increased expression, solubility, stability, and half-life (e.g. serum albumin, protein G, EBV-1 antigen), a specific affinity to simplify its isolation and purification (e.g. 

Figure 6.21. Stabilization of porcine mitochondrial MDH (mMDH) by bovine serum albumin (BSA). The half-life of mMDH at an incubation temperature of 42°C increases as the concentration of BSA in the medium is increased, but the increase in stability is correlated with a decrease in specific activity of the enzyme. (Figure modified after Lin et al., 2001.)...

The biosynthesis of serum albumin takes place in the liver. Normally, its half-life in the human being is 19 days, though this may change in response to disease or dietary availability of essential amino acids. It is interesting to note that rat serum albumin is biosynthesized in the form of "proalbumin," that is, the basic albumin molecule has attached to its N-terminus a peptide, Arg-Gly-Val-Phe-Arg-Arg, which is lost upon the secretion of the protein into the extracellular compartment. 

The half-life of a serum protein may be determined by plotting In SB versus t in Equation (20.2). Ln SB° is the y intercept, whereas k is the slope of the straight-line plot. The h/2 can also be read directly from the graph, as shown in Figure 20.3. Human IgG and serum albumin have half-lives of 8-12 and 7-10 days, respectively, whereas in rats, these figures are about 5 and 3 days. The half-life of albumin increases when dietary protein decreases, and excess dietary protein does the opposite. The half-life of IgG does not depend on dietary protein. 

The determination of SB° provides a means of estimating B. For instance, if a rat is injected with 5 mg radioactive serum albumin containing 150,000 dpm/mg and a subsequent plot of SB versus time is extrapolated to 1000 dpm/mg on the y axis, this means that the rat has a total of 5 x 150,000/1000, or 750 mg circulating serum albumin. If the rat weighs 250 g, the rat then has 3 mg albumin per g body weight. Half-life and pool determinations in circulation can be calculated for any substance, such as glucose, creatinine, or drugs. 

Pharmacokinetics Oral absorption of the drug increases when taken with food. It is extensively bound to serum albumin, and has a plasma half-life of 16 to 34 hours. Troglitazone is metabolized to several inactive metabolites, and can induce cytochrome P-450. The primary excretory route is in the feces. The drug is contraindicated in breast-feeding women. 

PEM is frequently associated with changes in serum markers such as protein, lipid, and nitrogen (Hendrickse, 1991). Decreased serum albumin levels have been used as a standard PEM indicator. Since albumin has a long half-life of 18 days in the plasma and a large pool size that decreases in various illnesses (such as hepatic insufficiency and nephrosis), it is not a specific marker for recent nutritional inadequacies. Prealbumin (or transthyretin), by virtue of its higher catabolic rate (half-life = 1.9 days) and small pool size, is a very sensitive and fairly specific indicator of acute malnutrition and shortterm responses to nutritional replacements in patients of all ages (Bernstein and Ingenbleek, 2002). 

Albumin is synthesised in the liver and has a long half-life of around 20 days. Mrs MW s low serum albumin is indicative of chronic liver disease. Albumin synthesis is also depressed in states of poor nutrition. 

The majority of albumin in the blood has been manufactured by the liver accordingly, serum albumin is a marker of the liver s synthetic capacity. Albumin has a half-life of about 20 days and therefore is used as an indicator of chronic disease. In cirrhosis, albumin production can fall by more than 50%, leading to serum levels as low as 20 g/L. A patient with acute liver failure is likely to have a normal albumin level initially. 

Albumin is synthesized in the liver cell. The rate of synthesis is 12—17 g/day (150-250 mg/kg BW), which can be enhanced 3—4 times due to a loss of albumin. The albumin pool of the organism is approx. 500 g. Half-life is 18—21 days. Albumin is determined as a part of serum electrophoresis either quantitatively (g/l or g/dl, respectively) or as a relative percentage (rel. %). Concentrations of globulins are also quantified in this way. 

Transferrin an iron-transport protein in the plasma, has a half-life of about 8 days thyroxine-binding protein, 2 days and retinol-binding protein, 0,4 days-Because of the relatively long half-life of albumin, the serum albumin level is not a particularly sensitive indicator of dietary protein status. Therefore, retinol-binding protein and thyroxine-binding protein have been used to assess malnutrition in poorly nourished populatiorrs. Note that these two proteins occur together as a complex in the bloodstream. 

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