ObjectiveTo 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 methodsBlood pressure, plasma lipids, platelet cytosolic calcium concentration ([Ca2+]i) and pH (pHi) together with thrombin-induced changes in these parameters as well as erythrocyte [Ca2+]iand45Ca 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.ResultsWith a low salt intake platelet pHiwas lower in SS/Jr than it was in SR/Jr rats, whereas basal platelet [Ca2+]iwas similar in rats of both strains. The difference in basal pHibetween SS/Jr and SR/Jr rats increased progressively with age of animals. A high salt intake from youth did not influence platelet [Ca2+]iin rats of either strain but it caused an earlier decrease in pHiin SR/Jr than it did in SS/Jr rats. Thrombin stimulation induced similar elevations of pHiand [Ca2+]iin rats of both strains, irrespective of age, salt intake and response of blood pressure to salt intake. Erythrocyte45Ca influx and [Ca2+]iwere greater for SS/Jr rats but only the latter parameter was correlated positively to blood pressure. Both regulation of platelet pHiand erythrocyte Ca2+handling were significantly related to plasma lipid levels.ConclusionsPlatelets of SS/Jr rats fed a low-salt diet were characterized by a lower basal cytosolic pHibut unchanged [Ca2+]irelative to those of SR/Jr rats. Hypertension induced by high salt intake was associated with increased erythrocyte [Ca2+]ibut not with elevation of platelet [Ca2+]ior alteration of response to stimulation with thrombin.