Erythrocyte,normal properties

The transport behavior of Li+ across membranes has been the focus of numerous studies, the bulk of which have concentrated upon the human erythrocyte for which the Li+ transport pathways have been elucidated and are summarized below. The movement of Li+ across cell membranes is mediated by transport systems which normally transport other ions, therefore the normal intracellular and subcellular electrolyte balance is likely to be disturbed by this extra cation. Additionally, Li+ has been shown to increase membrane phospholipid unsaturation in rat brain, leading to enhanced fluidity in the membrane, which could have repercussions for membrane-associated proteins and for membrane transport properties. 

Another procedure to increase the specificity of acid phosphatase determinations for prostatic disease has involved the use of n- (-I-) -tartrate to distinguish between the enzyme from the prostate and other tissues. In a series of papers from 1947 to 1949, Abul-Fadl and King (Al, A2, A3, A4) studied the properties of various acid phosphatases and reported that 0.01 Af L- (4-) -tartrate inhibited the hydrolysis of phenyl phosphate by human prostatic acid phosphatase dissolved in normal saline or in plasma to the extent of 95%, but had no effect on the hydrolysis by acid phosphatase from erythrocytes. The inhibitions of acid phosphatases from other human tissues were as follows liver, 70% kidney, 80% spleen, 70%. 

After intravenous administration of oxaliplatin, about 33% and 40% of the dose is bound to erythrocytes and plasma proteins. The half-life averages 26 days, which is in accordance with the normal life expectancy of erythrocytes (12-50 days). Oxaliplatin undergoes rapid non-enzymatic biotransformation to form a variety of reactive platinum intermediates, which bind rapidly and extensively to plasma proteins and erythrocytes. The antineoplastic and toxic properties appear to reside in the non-protein bound fraction, whereas platinum bound to plasma proteins or erythrocytes is considered to be pharmacologically inactive. Biotransformation produces DACH-platinum dichloride, 12-DACH-platinum dicysteinate, 1,2-DACH-platinum diglutathionate, 1,2-DACH-platinum mono-glutathionate, and 1,2-DACH-platinum methionine. The erythrocyte contains only thiol derivatives, whereas all derivatives can be recovered from the plasma. 

Pyrimidine-5 -nucleotidases are a group of enzymes dephos-phorylating pyrimidine nucleotides to the corresponding nucleosides. The pyrimidine bases diffuse out of the erythrocyte and the phosphates are retained. Pyrimidine phosphates are present on ribosomes of erythroblasts and reticulocytes, but there are normally no pyrimidines in mature RBCs. Two cytoplasmic forms of the enzyme were identified in the erythrocyte, P5 N-1 and P5 N-2. These enzymes are encoded by different genes and have different molecular properties and substrate specificities. Since there are no known disorders associated with deficiency of P5 N-2, this enzyme will not be further discussed here. 

Na, K-ATPase of human erythrocytes can respond to the stimulation of an ac field of approximately 20 V/cm to pump Na+, K+, and Rb+ against their respective concentration gradients. There was no irreversible damage of the membrane permeation barrier after the erythrocytes were exposed for several hours to this magnitude of ac field. After the field was turned off, the erythrocytes behaved very much like fresh erythrocytes in terms of their cell shape, volume, and normal ion permeation properties. 

One of the more interesting aspects of HPRT is that in the circulating red cell of normal subjects it is inactivated as a first-order reaction and its half-life can be determined (R4). The enzyme has a half-life of 88 days in the red cells of normal subjects that is, the catalytic property of the enzyme has a half-life of 88 days. Interestingly, if one determines the half-life of the enzyme in terms of the immunological properties, it turns out to be infinite, that is, despite the fact that the enzyme is denatured as a catalyst, the antigenic properties are not destroyed during the life of the red cell (Y2). Obviously, this is why the inactive enzyme in the erythrocytes of the deficient patients is the same as that in normal subjects since there is complete cross reactivity of catalytically active and inactive enzyme. 

Adediran SA. Kinetic properties of normal human erythrocyte glucose-6-phosphate dehydrogenase dimmers. Biochimie 1991 73 1211-1218. 

Waugh, R. and Evans, E.A. 1979. Thermoelasticity of red blood cell membrane. Biophys. J. 26 115-132. Waugh, R.E. and Marches , S.L. 1990. Consequences of structural abnormalities on the mechanical properties of red blood cell membrane. In Cellular and Molecular Biology of Normal and Abnormal Erythrocyte Membranes, C.M. Cohen and J. Palek, eds. pp. 185-199, Alan R. Liss, New York, NY. Yeung, A. and Evans, E. 1989. Cortical shell-liquid core model for passive flow ofliquid-like spherical cells into micropipets. Biophys. J. 56 139-149. 

Several properties of the erythrocyte enzyme were studied in order to further characterize the partial deficiency of APRT which was considerably less than 50% of normal values. A mixture of the hemolysate from the propositus with normal hemolysate resulted in the expected intermediate level of activity. This eliminates the possibility of the presence of an inhibitor or absence of an activator of the enzyme in erythrocytes. There was no evidence of increased enzyme lability. APRT from the propositus displayed a normal rate of thermal inactivation at 570C (Fig. 2). In addition, the apparent half-life of the enzyme in circulating erythrocytes in vivo from the propositus and an affected daughter was similar to the half-life of normal erythrocyte APRT (Fig. 3). The possible explanations for the markedly reduced erythrocyte APRT activity have become complex in the light of recent direct evidence that human erythrocyte APRT normally exists as a trimer composed of three... 

The Duarte gene [23] does not lead to disease but to a qualitatively altered erythrocyte Gal-l-P uridyl transferase with about half the normal activity and different electrophoretic properties. Other genes coded for qualitatively different Gal-l-P uridyl transferases are known some lead to disease, e.g. when the enzyme has low stability. 

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