Total exchangeable sodium in rats with mestranol-induced hypertension

Rats were fed a diet containing mestranol, an orally active estrogen, while control rats were fed the same diet without mestranol. After 6 months of these diets, the rats were weighed, blood pressures were measured, and total exchangeable sodium was determined by injecting 24Na and determining the amount of 24Na in the plasma, the plasma Na concentration, and the residual 24Na in each rat. The 16 mestranol-treated rats were hypertensive (mean arterial pressure 135 2 3 mm Hg) when compared with the 17 controls (116 f 3 mm Hg). Total exchangeable sodium in the mestranol-treated rats averaged 39.94 f 0.49 (SEM) mEq/kg body wt, which was very similar to the value of 39.87 f 0.63 mEq/kg found in the control rats. Thus, no changes in total exchangeable sodium in mestranol-hypertensive rats were found in these studies.