WATER AND ELECTROLYTE ALTERATIONS IN PLASMA, BRAIN AND LIVER OF RATS AFTER CASTRATION AND SEX HORMONE ADMINISTRATION

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Abstract
Ovariectomy, hypophysectomy and administration of estradiol, progesterone, testosterone or methylandrostenediol altered water or electrolyte concentrations in plasma, liver, cerebral cortex, brain stem and cerebellum in the rat. High daily doses of the steroids (500 [mu]g/100 g body weight) increased plasma sodium levels. Estradiol, followed by progesterone, then testosterone and methylandrostenediol, was most effective in producing hypernatremia. Lower doses of estradiol (10-200 ug/100 g body weight) did not change plasma sodium concentrations. Plasma potassium was increased by ovariectomy and decreased by low doses of estradiol in ovariectomized, but not in hypophysectomized rats. All doses of estradiol lowered per cent plasma water in intact adult male rats and ovariectomized adult females, but not in hypophysectomized rats. High doses of the steroids, especially of estradiol plus progesterone, raised concentrations of water, sodium, potassium and chloride in the liver, whereas water, sodium and potassium concentrations remained constant in brain. Each of the steroids elevated brain chloride concentrations. Of the brain areas analyzed, the cerebral cortex most consistently showed increased chloride after injections. Testosterone and progesterone, followed by estradiol and then methylandrostenediol, were most potent in increasing brain chloride concentrations. Because the sex hormones have previously been shown to alter brain excitability, it is postulated that some of these alterations may be correlated with concomitant changes in brain anionic concentrations.