Ca2+ transport in unstimulated platelets of essential hypertensives and their blood relatives

OBJECTIVE:Intracellular free Ca concentration has been shown to be elevated in platelets from essential hypertensive patients. This study was designed to characterize Ca homeostasis in platelets of essential hypertensives. DESIGN:A double-blind study was carried out. Untreated and treated (propranolol therapy) essential hypertensives were studied in comparison with normotensive control subjects. First-degree blood relatives of essential hypertensives were also studied. The various procedures used in the study were already standardized and well-established methods. METHOD:For Ca uptake and efflux studies, Ca was used. For intracellular free Ca concentration studies the fluorescent Ca chelator dye fura-2/acetoxymethyl ester (fura-2/AM) was used. RESULTS:The uptake of Ca by unstimulated platelets of untreated essential hypertensives and their relatives was significantly higher than for controls. However, essential hypertensives treated with a β-blocker drug showed no significant difference in Ca uptake compared with controls. A significantly decreased Ca efflux was observed in essential hypertensives (both untreated and treated) compared with controls. Relatives also showed a depressed Ca efflux compared with controls. CONCLUSIONS:It appears that the elevated intracellular free Ca concentration levels in platelets (also observed by us) may be due to both an enhanced uptake into, and decreased efflux of Ca from, the cell. Beta-blocker therapy may help to normalize the elevated intracellular free Ca concentration levels observed in essential hypertensives. Relatives exhibit a state predisposed towards the development of hypertension.