The assay of oestrogenic activity of Trifolium subterraneum L. by increase in uterine weight in the spayed guinea pig. I. Characteristics of the dose-response relationship

When graded doses of clover were consumed over a period of eight hours on each of two days by animals weighing 350-520 g. which had been spayed from 19 to 23 days, the uterine weight 50 to 52 hours after feeding began was related to the amount of clover consumed. In 29 of the series of observations in which clover was fed at different dose levels, the corresponding means of the logarithm of the uterine weights in decigrams (log u.dg.) were either distributed in equal numbers about 0.75 or most were greater than 0.75. The data relating the logarithm of the dose in grams (log d.g.) to log u.dg. from these 29 series were well fitted by a straight line over the range log u.dg. = 0.75 to 0.90, and they possessed such characteristics that the log d.g., log u.dg. relationship may be taken as affording a satisfactory basis for comparing, with definable limits of error, the relative activities, presumably oestrogenic, of most samples of clover. When graded doses of hexoestrol were administered orally under similar conditions to the clover, the weight of the uterus was also related to the dose administered, and the data relating log dose and log uterine weight were fitted by a straight line with a regression coefficient of a similar order. No increase in weight of the uterus followed oral administration of doses as great as 20 mg. of testosterone or progesterone.