PH of plasma

Measurement of free t-PA in plasma presents challenges in terms of preventing t-PA from complexing to PAI-1 released from platelets after blood collection. To dissociate any preformed t-PA-PAI-1 complex, the anticoagulant pH has to be close to 3.0. Even if blood is collected with an acidic anticoagulant, the blood pH will rise because of the powerful buffering action of hemoglobin. Thus, the pH of plasma has to be adjusted to 3.0 in order to dissociate the t-PA-PAI-I complex (115). 

Unlike urine, plasma contains about 7% proteins and a substantial amount of lipids, salts, and enzymes, especially esterases. The pH of plasma is approximately 7.4. Despite its complex nature, plasma exhibits a composition that hardly varies within the animal species and the diet, except for the lipid content, which is diet-dependent. 

The salts of the buffer pairs responsible for control of the pH of plasma and extracellular fluid involve sodium as the principal cation, while the cellular buffers involve potassium salts. See also Acid-Base Regulation (Blood) and Diuretic Agents. 

The equilibrium between plasma and red cells has been disturbed by the reactions described so far. The concentration of HCO3 has increased relatively more in the erythrocytes than in the plasma the pH of plasma has fallen relatively more than the pH of the erythrocytes and the non-difftisible ion concentration in the erythrocytes has fallen because of the increase in protonation of proteins and hemoglobin. The membrane potential of the erythrocytes therefore becomes less negative, and the distribution of all diffusible ions must change in accordance with the new membrane potential. The ion shifts that occur rapidly are a movement of HCO3 out of the erythrocytes and a movement of Cr into the erythrocytes to provide electrochemical balance. This shift of chloride ions is referred to as the chloride shift (Figure 46-9, reactions 6 and 7). As a result of these ion fluxes, the concentration of chloride in the venous plasma is about 1 mmol/L lower than that in the arterial plasma. 

Rose bengal is colored at the pH of plasma with an absorption peak at 545 m/A (S30). However, the absorption spectrum is affected by absorption of dye on albumin so that, in diluted plasma, the absorption peak is at 560 rufi (S2). 

Sample preparation Condition a Bond-Elut C2 SPE cartridge with 2 mL MeOH and 2 mL water. Adjust pH of plasma to 1.0 with dilute phosphoric acid, add 1 mL to the SPE cartridge, wash with pH 1.0 dilute phosphoric acid, wash with water, wash with EtOH, wash with MeCN, air dry, elute with 200 p,L mobile phase, inject tm aliquot. 

Sample preparation Adjust pH of plasma to 4-5 with phosphoric acid (about 30 jlL phosphoric acid per 4 mL of plasma). 500 p,L Acidified plasma -I- 100 xL 2 pg/mL flurbiprofen in MeCN water 30 70 - 1.3 mL MeCN, vortex, centrifuge at 1000 g for 15 min. Remove the supernatant and add it to 800 pL 1 M pH 3.0 glycine buffer and 4 mL ethyl acetate, shake horizontally at 70 rpm for 15 min, centrifuge at 1000 g for 15 min. Remove the organic layer and evaporate it to dryness in an evacuated centrifuge, reconstitute the residue in 250 xL mobile phase, inject a 10-100 gL aliquot. 

Which will pass most readily from plasma into the brain (pH of plasma, 7.3). Answers at end of this chapter. 

Sample preparation AcUust pH of plasma to 4-5 with phosphoric acid (about 30 (xL phosphoric acid per 4 mL of plasma). 500 p,L Acidified plasma -I- 100 p,L 2 (xg/mL flurbiprofen in MeCN water 30 70 1.3 mL MeCiN, vortex, centrifuge at 1000 g for 15 min. Remove... 

Blood is a complex non-Newtonian fluid that consists of several kinds of cells carried through the circulation in an isotonic aqueous medium, the plasma. Plasma contains a large number of proteins, salts, lipids, and various other nutrients and components. The cellular components normally account for 45% of the total blood volume. They include erythrocytes, leukocytes, and platelets. Erythrocytes constitute most of the total cell volume 1% is accounted for by leukocytes, which include several types of cells. The major blood cell types and their concentrations are shown in Table 1. About 52% of total blood volume is water and the remaining 3% is contributed by dissolved solids, including protein and nonprotein components. The normal pH of plasma is 7.4. 

Titratable acidity is determined by titration of aliquots of the gastric juice sample with O.ImolH NaOH to neutrality. Although neutrality has been traditionally set at pH 7.0, the physicochemical point of neutrality, others have recommended titration to pH 7.4, the pH of plasma. This issue remains unsettled. The amount of NaOH (in mmolH ) used for titration to neutrality (pH 7.0) is the titratable acidity. 

In this condition, all metabolic functions of the kidney are depressed these functions include tubular secretion of hydrogen ions, reabsorption of bicarbonate ions and production of ammonia. In a subject with impaired renal function, the urine can scarcely be concentrated or diluted by comparison with plasma, its pH can be only slightly lowered below or raised above the pH of plasma and, because of lack of ammonia synthesis, the excretion of acid is profoundly depressed. The kidney can no longer perform its homeostatic regulatory role. Such a patient consuming a normal diet becomes progressively more acidotic because of the release of acid resulting from the metabolism of protein (Chapter 5). 

Samples (1.0 ml each) of a pool of pregnancy plasma were shaken at 37 C in polythene test-tubes with 0.1 ml of a suspension of Enzite-trypsin, an insoluble trypsin coupled to agarose (Miles Laboratories Ltd.). At various intervals the Enzite-trypsin was removed by centrifugation, 0.5 ml of the supernatant plasma was removed, dialysed against pH 7.0 assay-buffer and assayed renin. Figure 3 shows that pretreatment with trypsin resulted in an increase in renin concentration. If pH 7.4 phosphate buffer was incubated with Enzite-trypsin, the trypsin-free supernate assayed, no renin activity was present. This indicates that the increase in renin concentration after treatment with trypsin was not due to an effect of residual trypsin on the renin assay system. The pH of plasma after 24 hr incubation with trypsin was 7.6. Loss of renin activity occurred in the plasma incubated at 37°C without trypsin. 

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