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PubMed1986

Effects of halothane on transport of 5-hydroxytryptamine by platelet membranes.

Na+-dependent uptake of 5-HT (5-hydroxytryptamine) into plasma membrane vesicles derived from bovine blood platelets and ATP-dependent 5-HT uptake into storage vesicles in platelet lysates were measured. Na+-dependent uptake was temperature-dependent, inhibited by imipramine and exhibited Michaelis-Menten kinetics (apparent Km, 0.12 +/- 0.02 microM; Vmax. 559 +/- 54 pmol/min per mg of protein. Halothane had no effect on Na+-dependent transport of 5-HT in plasma-membrane vesicles. ATP-dependent 5-HT transport into storage granules also exhibited Michaelis-Menten kinetics (apparent Km 0.34 +/- 0.03 microM; Vmax. 34.3 +/- 1.7 pmol/min per mg of protein) and was inhibited by noradrenaline (norepinephrine), but not by imipramine. Exposure of the granules to halothane resulted in a progressive decrease in Vmax. The results demonstrate a possible site for disruption of platelet function by anaesthetics.

Adenosine Triphosphate↗

PubMed1983

Species-dependent variations in erythrocyte membrane skeletal proteins.

Two mammalian species (porcine and murine) have erythrocytes that are being widely used to study membrane protein synthesis and red cell aging. Erythrocytes of these species however, are significantly smaller than those of the human. Before results obtained from study of these red cells can be applied to human cells, the membrane skeleton of these species must be investigated to determine if the skeletal elements are equivalent. Both pig and mouse bands 4.1b were of lower molecular weight than human 4.1b, and the a/b ratio was lower. In each species, 4.1a and b were sequence-related phosphoproteins, and yielded substantially different one-dimensional peptide maps. Band 3 of pig and mouse erythrocytes had a higher molecular weight than human band 3 and also had differing one-dimensional peptide maps after limited proteolytic cleavage with three different enzymes. In each species, free band 3 and band 3 bound to the membrane skeleton had identical peptide maps. Other major membrane skeletal components (spectrin, actin, and bands 2.1 and 4.2) seem to be very similar in molecular weight in various species. These results demonstrate that the molecular weights and relative proportions of the membrane skeletal elements are species dependent.

Animals↗