Alterations of cytosolic calcium in platelets and erythrocytes of lyon hypertensive rats

Platelet cytosolic free calcium concentration ([Ca 2+ ] i ) and intracellular pH (pH i ) (including their responses to thrombin), as well as erythrocyte [Ca 2+ ] i and 45 Ca 2+ influx, were studied in Lyon hypertensive (LH) and normotensive (LN) rats aged 3 months. Platelets of LH rats were characterized by substantially elevated basal [Ca 2+ ] i values, higher [Ca 2+ 1 i levels after thrombin stimulation, and enhanced initial rate of thrombin-induced Mn 2+ entry through receptor-operated Ca 2+ channels. Basal platelet pH i values were not significantly different in LH and LN animals but thrombin elicited a significant alkalinization only in LH platelets. Erythrocytes of LH rats had an enhanced initial rate of 45 Ca 2+ and tended to elevated [Ca 2+ ] i levels. Our data indicate profound alterations in cell Ca 2+ handling in platelets and erythrocytes of LH rats, similar to those previously described in spontaneously hypertensive rats of the OkamotoAoki strain. The analysis of the relations between blood pressure, plasma lipids, and cell Ca 2+ handling suggested that triglycerides, but not cholesterol, might be involved in altered platelet Ca 2+ handling in LH rats.