Aggregation, membrane potential, and transport in platelets of spontaneously hypertensive rats

Aggregation, plasma membrane potential, and calcium uptake by platelets of spontaneously hypertensive rats (SHR) were studied. The sensitivity of SHR platelets to the action of ADP and collagen was increased. The addition of Ca-ionophore (A-23187) resulted in aggregation of SHR platelets at a Ca2+ concentration in the incubation medium 20%-30% lower than that required for aggregation of platelets from normotensive rats. The plasma membrane of SHR platelets was found to be partially depolarized (by 8-10 mV) as compared to that of normotensive controls. This difference was apparently due to a higher membrane permeability for Na+. It is suggested that the increase in 45Ca uptake by SHR platelets is related to an increased rate of Ca2+ diffusion along a potential-dependent channel, due to partial depolarization of plasma membrane.