valinomycin and Hypertension

After the addition of valinomycin into the incubation medium, the potassium content of rat erythrocytes rapidly decreases. The rate-limiting step of this reaction is a unidirectional efflux of anions through band 3 protein. The rate of this efflux in erythrocytes of spontaneously hypertensive rats (SHR) of the Wistar-Kyoto strain, is not altered. The loss of KCl by rat erythrocytes is accompanied by a decrease in intracellular water, cell shrinking and activation of Na+-H+i exchange. The rate of Na+-H+ exchange in the erythrocytes of SHR in the pre-hypertensive stage (4 weeks old) was decreased by 30%. There were no differences between 14-week-old and 28-week-old SHR and normotensive Wistar-Kyoto (WKY) rats. The half-maximal increase of the valinomycin-induced Na+-H+ exchange in erythrocytes of 14-week-old WKY and SHR was observed at KCl concentrations in the incubation medium of 25 and 40 mmol, respectively. The addition of activators of protein kinase A (dibutyryl-cAMP) or protein kinase C (beta-phorbol ester) resulted in an increase in the maximal rate of Na+-H+ exchange, and did not modify its dependence on K+o concentration. In all groups of SHR, the rate of valinomycin-induced H+ efflux from erythrocytes in the sodium-free medium was 1.5-2.5-fold higher than in age-matched WKY. Under these conditions (addition of valinomycin and inhibition of Na+-H+ exchange), haemoglobin release from erythrocytes of SHR, treated with hypotonic solution, was significantly decreased. We conclude that these differences are due to the alteration of the skeleton protein organization in the erythrocyte membranes of SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Biological Transport; Erythrocytes; Hemolysis; Hypertension; Hypotonic Solutions; Male; Potassium; Protein Kinases; Protons; Rats; Rats, Inbred SHR; Rats, Inbred Strains; Sodium; Valinomycin

The dependence of the rate of valinomycin-induced Na+/H+ erythrocyte metabolism on the extracellular K+ concentration has been investigated. It has been established that Na+/H+ metabolism in the erythrocytes of spontaneously hypertensive rats (SHR) is induced at higher [K+]o concentrations than in normotensive controls (WKY). The distinctions in the maximum rate of Na+/H+ metabolism were revealed only in SHR in pre-hypertensive stage (it was 20% lower than in WKY). It is suggested that the distinctions are determined by peculiarities of membrane cytoskeleton formation. The conclusion was confirmed in experiments on erythrocyte stability to orthovanadate effect.

Topics: Amiloride; Animals; Erythrocyte Deformability; Erythrocytes; Hydrogen; Hypertension; Male; Potassium; Rats; Rats, Inbred SHR; Rats, Inbred Strains; Rats, Inbred WKY; Sodium; Valinomycin; Vanadates

Introduction of valinomycin into erythrocyte incubation medium increased the cell stability to water-induced hemolysis. In these conditions the erythrocytes of spontaneously hypertensive and normotensive (control) rats release 63.2 +/- 1.5% and 80.9 +/- 1.6%, respectively, of the total hemoglobin content. Valinomycin effect is completely abolished with K+ substitution for Na+ and is independent of extracellular Ca2+ concentration. Valinomycin had no effect on human erythrocyte osmotic stability. It has been shown that valinomycin-induced kinetics of Na+ and K+ redistribution was different in human and rat erythrocytes. The distinctions are thought to be related to specific anion transport mediated by the third band protein--the main component of membrane cytoskeleton.

Topics: Animals; Calcium; Hypertension; Kinetics; Male; Osmotic Fragility; Potassium; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Sodium; Valinomycin