Cytosolic calcium in platelets of spontaneously hypertensive rats

To test the hypothesis that an abnormality of the intracellular concentration of ionized calcium, [Ca²⁺]_i, is associated with high blood pressure, we measured [Ca²⁺]_i in the platelets of spontaneously hypertensive (SHR) and Wistar-Kyoto control (WKY) rats using the Quin 2 technique after separation of the platelets in calcium-free medium, during calcium repletion, and upon exposure to agonists which increase platelet [Ca²⁺]_i(thrombin, adenosine diphosphate, serotonin and ionomycin). Despite clear-cut changes in [Ca²⁺]_i during these manipulations, there were no differences between the SHR and WKY rats in baseline levels of [Ca²⁺]_i or in the kinetics of changes in [Ca²⁺]_i. These results do not support the hypothesis that high levels of [Ca²⁺]_i at rest or abnormal kinetics of changes in [Ca²⁺]_i play a pathophysiological role in the hypertension of SHR.