Dietary salt decreases cytosolic calcium in platelets from Dahl salt-sensitive rats

To determine whether abnormal cellular Ca2+ handling is involved in salt-induced hypertension of Dahl salt-sensitive rats (DS), we investigated Ca2+ handling in fura 2-loaded platelets of DS and Dahl salt-resistant rats (DR) fed a high-NaCl (8%) or a low-NacL (0.3%) diet for 4 wk from 5 wk of age. At 5 wk of age, blood pressure, resting cytosolic Ca2+ concentration ([Ca2+]i), the thrombin-evoked increase in [Ca2+]i and the size of internal Ca2+ stores of DS were comparable with those of DR. After 4 wk on the diets, resting [Ca2+]i of DS on high-NaCl diet was lower than that of DS on low-NaCl diet, and there was no effect of high salt intake on resting [Ca2+]i in DR. In DS, high salt intake attenuated the [Ca2+]i response to thrombin in the presence of external Ca2+. In contrast, the [Ca2+]i response to thrombin in the absence of external Ca2+ was enhanced by high salt intake in DS. The size of internal Ca2+ stores was increased by high salt intake in DS but not in DR. These data suggest that it is not obligatory for hypertension to be accompanied by an increase in platelet [Ca2+]i.