Calcium-related abnormalities in lymphocytes from genetically hypertensive rats.

We examined the effect of various external calcium concentrations on net potassium efflux and net sodium influx in lymphocytes from spontaneously hypertensive rats (SHR), stroke-prone spontaneously hypertensive rats (SHRSP), and Wistar-Kyoto rats (WKY). Net potassium efflux was greater in lymphocytes from SHRSP than in those from WKY at external calcium concentrations of 0.1, 0.3, 1.0, and 3.0 mM but not at 0 mM (14.9 +/- 0.8 vs 13.0 +/- 0.7 mmol per kilogram of dry weight per hour, respectively). Net sodium influx in lymphocytes from SHRSP was greater than in those from WKY at all external calcium concentrations tested (0, 0.1, 1.0, and 3.0 mM). In contrast to lymphocytes from WKY, net potassium efflux and net sodium influx in lymphocytes from SHRSP were not significantly higher at 0 than at 0.1 mM external calcium concentration. Lymphocytes from SHRSP had elevated intracellular free calcium concentrations (173.6 +/- 7.4 nM, n = 8), as compared with lymphocytes from WKY (98.1 +/- 9.1 nM, n = 8). These data suggest that the interaction of calcium with the lymphocyte plasma membrane directly affects monovalent ion permeability and is altered in lymphocytes from SHRSP, as compared with those from WKY. Our findings support the hypothesis that in hypertension there is a generalized increase in cell membrane permeability to calcium and monovalent ions, which may result from a reduced number of calcium-binding sites on the plasma membrane.