ALTERATIONS OF CYTOSOLIC CALCIUM IN PLATELETS AND ERYTHROCYTES OF LYON HYPERTENSIVE RATS

Platelet cytosolic free calcium concentration ([Ca2+](i)) and intracel lular pH (pH(i)) (including their responses to thrombin), as well as e rythrocyte [Ca2+](i) and Ca-45(2+) influx, were studied in Lyon hypert ensive (LH) and normotensive (LN) rats aged 3 months. Platelets of LH rats were characterized by substantially elevated basal [Ca2+](i) valu es, higher [Ca2+](i) levels after thrombin stimulation, and enhanced i nitial rate of thrombin-induced Mn2+ entry through receptor-operated C a2+ channels. Basal platelet pH(i) values were not significantly diffe rent in LH and LN animals but thrombin elicited a significant alkalini zation only in LH platelets. Erythrocytes of LH rats had an enhanced i nitial rate of Ca-45(2+) and tended to elevated [Ca2+](i) levels. Our data indicate profound alterations in cell Ca2+ handling in platelets and erythrocytes of LH rats, similar to those previously described in spontaneously hypertensive rats of the Okamoto-Aoki strain. The analys is of the relations between blood pressure, plasma lipids, and cell Ca 2+ handling suggested that triglycerides, but not cholesterol, might b e involved in altered platelet Ca2+ handling in LH rats.