CYTOSOLIC PH AND CALCIUM IN DAHL SALT-SENSITIVE AND SALT-RESISTANT RATS - THE RELATIONSHIP TO PLASMA-LIPIDS

Objective To search for alterations of cytosolic pH and cell calcium h andling in platelets and erythrocytes of Dahl rats susceptible and res istant to salt-induced hypertension. Design and methods Blood pressure , plasma lipids, platelet cytosolic calcium concentration ([Ca2+](i)) and pH (pH(i)) together with thrombin-induced changes in these paramet ers as well as erythrocyte [Ca2+](i) and Ca-45 influx were determined in Dahl salt-sensitive (SS/Jr) and salt-resistant (SR/Jr) rats aged 9, 15 and 24 weeks, which were fed a low-salt diet (0.3% NaCl), and in a nimals fed high-salt diet (4% NaCl) for 5-10 weeks since weaning. Resu lts With a low salt intake platelet pH(i) was lower in SS/Jr than it w as in SR/Jr rats, whereas basal platelet [Ca2+](i) was similar in rats of both strains. The difference in basal pH(i) between SS/Jr and SR/J r rats increased progressively with age of animals. A high salt intake from youth did not influence platelet [Ca2+](i) in rats of either str ain but it caused an earlier decrease in pH(i) in SR/Jr than it did in SS/Jr rats. Thrombin stimulation induced similar elevations of pH(i) and [Ca2+](i) in rats of both strains, irrespective of age, salt intak e and response of blood pressure to salt intake. Erythrocyte Ca-45 inf lux and [Ca2+](i) were greater for SS/Jr rats but only the latter para meter was correlated positively to blood pressure. Both regulation of platelet pH(i) and erythrocyte Ca2+ handling were significantly relate d to plasma lipid levels. Conclusions Platelets of SS/Jr rats fed a lo w-salt diet were characterized by a lower basal cytosolic pH(i) but un changed [Ca2+](i) relative to those of SR/Jr rats. Hypertension induce d by high salt intake was associated with increased erythrocyte [Ca2+] (i) but not with elevation of platelet [Ca2+](i) or alteration of resp onse to stimulation with thrombin. (C) Rapid Science Publishers ISSN 0 263-6352.