[Aggregation, membrane potential and Na+ and Ca2+ in the thrombocytes of rats with spontaneous hypertension]

Platelet aggregation, plasmatic membrane potential and sodium and calcium uptake were investigated in spontaneously hypertensive rats (SHR). The sensitivity of SHR's platelets to effects of all aggregational agents examined (ADP, collagen, ADP + noradrenaline) was enhanced. Ca-ionophore A 23187 caused complete SHR platelet aggregation when Ca2+ concentration in the incubation medium was 20-30% below the level of normotensive control specimens. The membrane potential of SHR platelets was reduced by 8-12 mV, which may be attributed to increased content of metabolizing sodium as well as a higher rate of its transmembrane exchange. A higher rate of Ca2+ uptake by SHR platelets may be related to partial depolarization of the membrane and the cation's diffusion along potential-dependent Ca-channels.