Concentrations of ionic and total calcium in plasma of four models of hypertension.

The levels of ionic calcium in whole blood obtained from female Sprague-Dawley (SDR). Wistar-Kyoto (WKY), and spontaneously hypertensive (SHR) rate tended to decrease between 5 and 13 wk of age. During this interval the plasma total calcium levels of each strain remained stable, indicating an increase in the binding or complexing of endogenous calcium with maturation. The ionic calcium levels of WKY were lower than those of SDR, while SHR levels were below those of the WKY and SDR strains. Neither the one-kidney, one-clip (1KHT) nor the two-kidney one-clip (2KHT) renovascular models of hypertension showed evidence of an alteration in blood ionic or total calcium concentrations compared with sham-operated controls. The ionic calcium levels of blood from deoxycorticosterone-treated (DOCA/saline) hypertensive rats were significantly reduced from those of sham-operated controls but were similar to values recorded for normotensive uninephrectomized controls. Each of the four models of hypertension studied and the normotensive uninephrectomized control group demonstrated some degree of reduction in the in vitro binding or complexing of exogenous calcium. The results indicate that the spontaneous, renovascular, and mineralocorticoid forms of hypertension examined were accompanied by some disturbance in extracellular calcium homeostasis. It is unlikely, however, that the alterations observed are primary causal factors in the maintenance of high blood pressure.