1. The cytoplasmic free calcium concentration ([Ca2+]i) was assessed with the fluorescent dye Quin 2 in platelets and lymphocytes of spontaneously hypertensive rats (SHR), normotensive Wistar—Kyoto rats (WKY), essential hypertensive patients (EHP) and normotensive human control subjects (NCS).
2. [Ca2+]i was significantly higher in the platelets of 8- and 20-week-old SHR in comparison with WKY. However, no difference was evident after weaning. Changes of cellular calcium in hypertensive rats apparently evolved simultaneously with the development of high arterial pressure.
3. [Ca2+]i was significantly higher in platelets of EHP than in NCS.
4. In lymphocytes of SHR, [Ca2+]i was not different from WKY at 4 and 8 weeks, but was increased at 14 weeks and at older ages. In EHP, intralymphocytic [Ca2+] was only modestly higher than in controls. On the whole, the results suggest that control of cytoplasmic calcium in these blood cells is similarly affected in human and animal models of primary hypertension.