The Effects of Estrogens on Sodium and Potassium Metabolism in Rats

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Abstract
Male Wistar rats, housed in individual metabolism cages and fed standard rat chow, received, after a 2-wk acclimation period, daily i.m. injections of 17.beta.-estradiol (0.17 .mu.g/g body weight) in peanut oil or 0.1 ml peanut oil alone for 4 days. Water and food intake were measured daily, as were urinary volume and electrolytes. 17.beta.-estradiol administration resulted in significant decreases in food and Na and K intake and in urinary Na and K excretion. In a 2nd series of experiments, male rats treated with 17.beta.-estradiol or peanut oil as above had access to Na-free food, water and saline. In this group of animals, 17.beta.-estradiol administration resulted in a significant decrease in food intake but no significant changes in Na intake or excretion. K intake and excretion decreased as above. In a 3rd experiment, Na intake and output in female rats on standard rat chow correlated with the phase of the estrous cycle, being lowest during proestrus and estrous and highest during metestrus and diestrus. 17.beta.-estradiol reduces the renal excretion of Na and K primarily as a consequence of a reduction in food intake and exerts no specific effect on either Na or K metabolism.