COMPARATIVE EFFECTIVENESS OF ESTROGENS ON FLUID IMBIBITION AND GROWTH OF THE RAT'S UTERUS1

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Abstract
Five natural estrogens (estradiol-17B, estrone, estriol, equilin and equilenin) and one synthetic estrogen (diethylstilbestrol) were compared as to effectiveness in promoting fluid imbibition and growth of the uterus in 22-day old rats. Graded amounts of each estrogen were injected sub-cutaneously as a single dose in 0.1 cc. sesame oil and uterine responses observed at intervals up to 72 hours. Both quantitative and qualitative differences were found with respect to dose required for a response and speed, duration, and extent of the reaction. Some estrogens are more effective for fluid imbibition and others more active for growth and superiority for one does not imply superiority for the other. It was found that the minimal dose in micrograms required to produce 33 1/3% increase in uterine wet weight at six hours (Astwood unit) is for estra-diol, 0.025; estriol, 0.029; diethylstilbestrol, 0.078; equilin, 0.312; estrone, 0.45; and equilenin, 0.546. The dosage required to produce 70% gain in uterine wet weight at six hours is estriol, 0.078; estradiol, 0.1; diethylstilbestrol, 0.156; equilenin, 0.625; estrone and equilin, 1.25. The dose at which maximal imbibition occurs at four hours rather than at six hours is estriol, 0.039; estradiol, 0.15; diethylstilbestrol, 0.625; equilin, 5; and equilenin and estrone, 50.0. The order of potency for uterine growth between the thirtieth and fortieth hours by the dose required for maximal fluid imbibition on the sixth hour was found to be diethylstilbestrol, 0.1; estradiol, 0.1; equilin, 1.25; estriol, 5.0; estrone, 1.25; and equilenin, 1.25. While the order of effectiveness for growth at large doses, up to 50 [mu]g., was diethylstilbestrol, estradiol, equilin, estrone, equilenin and estriol.

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