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 handling in platelets and erythrocytes of Dahl rats susceptible and resistant 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 parameters 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 animals fed high-salt diet (4% NaCl) for 5-10 weeks since weaning. Results With a low salt intake platelet pH(i) was lower in SS/Jr than it was 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/Jr rats increased progressively with age of animals. A high salt intake from youth did not influence platelet [Ca2+](i) in rats of either strain 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 intake and response of blood pressure to salt intake. Erythrocyte Ca-45 influx and [Ca2+](i) were greater for SS/Jr rats but only the latter parameter was correlated positively to blood pressure. Both regulation of platelet pH(i) and erythrocyte Ca2+ handling were significantly related to plasma lipid levels. Conclusions Platelets of SS/Jr rats fed a low-salt diet were characterized by a lower basal cytosolic pH(i) but unchanged [Ca2+](i) relative to those of SR/Jr rats. Hypertension induced by high salt intake was associated with increased erythrocyte [Ca2+](i) but not with elevation of platelet [Ca2+](i) or alteration of response to stimulation with thrombin. (C) Rapid Science Publishers ISSN 0263-6352.