BIOASSAY OF ESTROGENS USING THE MOUSE UTERINE RESPONSE1

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Abstract
A precise, convenient, and inexpensive method has been descr. for the assay of 3 naturally occurring estrogens. It is based on the straight line relationship between the logarithm of the dose and the uterine wt. response of the immature mouse. When the assay is set up according to the statistical design of Bliss (1944), using a total of 40 mice, 20 on unknown and 20 on standard, the standard error of the potency ratio detd. is [plus or minus] 13% and lambda is approx. 0.18. A wide range of estrone concn. can be used if the log dose-log response relationship is employed. Estrone and alpha-estradiol give parallel curves over the ranges of 0.1-0.32 [mu]g. for estrone and 0.02-0.06 [mu]g. for alpha-estradiol. The potency of alpha-estradiol relative to estrone is 5.41. Estriol, in the range from 1-4 [mu]g., and estrone, in the range from 0.04-0.08. [mu]g. also give parallel curves. The potency of estriol relative to estrone at this response level is 0.05. At higher levels of response, in the range for estrone of 0.1-0.32 [mu]g. and for estriol of 2.16[mu]g., the curves differ in slope, and estriol must be assayed against an estriol standard. Amts. less than 0.02 [mu]g. of estradiol, equal to 0.04[mu].g. of estrone, and to 2[mu]g. of estriol can be detd. by this method. The method has been applied to urinary extracts with satisfactory results.