Fura-2 used as a probe to show elevated intracellular free calcium in platelets of Dahl-sensitive rats fed a high salt diet.

Elevated intracellular free calcium concentration [Ca2+]i in vascular smooth muscle cells has been implicated in the pathophysiology of hypertension. Platelet [Ca2+]i was measured using the fluorescent indicator, Fura-2, in Dahl sensitive (DS) and resistant (DR) rats given high (8% NaCl) and low (0.4% NaCl) salt diets, as well as in the spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats. The aim of this study was to show whether [Ca2+]i is elevated in salt induced hypertension. Platelet [Ca2+]i and systolic blood pressure (SBP) were higher (p less than 0.001) in DS rats given a high than low salt diets. In contrast, no changes in platelet [Ca2+]i and SBP were observed in DR rats. In SHR, platelet [Ca2+]i and SBP were higher (p less than 0.001) than in the WKY rats. Platelet [Ca2+]i correlated with SBP in all groups of rats (r = 0.929; p less than 0.001, n = 38). The parallel increase in SBP and [Ca2+]i in the DS high salt rats and the SHR suggests that an increased [Ca2+]i is involved in the pathophysiology of hypertension in the two models which differ with respect to the pathogenesis of their hypertension. This increase in [Ca2+]i therefore seems to reflect an abnormality in [Ca2+]i handling in hypertension regardless of its cause.