OVARIAN HORMONES AND THE IONIC BALANCE OF UTERINE MUSCLE

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Abstract
In order to determine the K:Na ratio in uterine muscle, castrated mature females or infantile non-castrated females of New Zealand White rabbits were divided into 3 groups, labeled "estrogen," "estrogen withdrawal" and "progesterone". Each group received daily injections of 25 [mu]g natural estrogens in oil or 25 [mu]g estradiol benzoate intramuscularly for 7-8 days in castrated females and for 12-15 days in infantile females. The estrogen group was killed at the end of the treatment period, the estrogen-withdrawal group 3-4 days after the last estrogen injection, and the progesterone group received 1 mg progesterone in oil daily for 3-4 days after the estrogen treatment. After intravenous anesthetization of the animals, the uterus was removed and divided into 0.1-0.4 g samples, of which 2-3 were used for determined of dry weight and Na and K concentrations, and 2-4 for determination of inulin space. The uterine muscle proper (isolated myometrium) was separated from the endometrium and divided into 0.1-0.7 g samples for determination of Na and Cl space, dry weight and Na and K content. The dry weight group averages for whole uteri were 15.8 and 17.6 for the estrogen and progesterone groups, respectively, and for the isolated myometrium, 16.1, 17.0 and 15.7 for the estrogen, estrogen-withdrawal and progesterone groups, respectively. For the whole uterus there was a significant difference between the estrogen and progesterone groups with respect to extracellular water (ECW), Na and K. For the isolated myometrium there was no significant difference between the estrogen-withdrawal and the progesterone groups with respect to ECW, but both were significantly lower than the estrogen group. The Na concentration of the estrogen and progesterone myometrium were not significantly different, but both were significantly higher than the estrogen-withdrawal group. The K concentration of the estrogen-withdrawal muscle was significantly different from that of the progesterone muscle and significantly lower than that of the estrogen muscle. The intracellular ion concentrations calculated from these results indicated that progesterone muscles had a higher intracellular Na concentration and a lower intracellular K concentration than estrogen muscles. The intracellular K:Na ratio was higher (5.3) for the estrogen than for the progesterone muscles (2.9). Comparison of the whole uterus with the isolated myometrium indicated that the Na concentration of the estrogen endometrium was the same as that of the myometrium, but the ECW and K were significantly less. The ECW of the progesterone endometrium was more, Na concentration less and K concentration the same as in the myometrium. Regardless of the assumed proportional weight of the endometrium, the estrogen contained more Na and less K than the progesterone, the ratio of intracellular K to Na being 2.8 or less for the estrogen and 6.2 or more for the progesterone. The endometrium therefore, accumulates K more efficiently under progesterone than under estrogen domination, indicating that selective K accumulation depends both on the qualities of the tissue and on the dominating ovarian hormone.

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