Abstract
SUMMARY The response to gonadotrophins in an assay based on the induction of ovulation in immature mice was reduced by treatment of the experimental animals with barbitone. The responses to follicle-stimulating hormone and luteinizing hormone (LH) were reduced to a similar degree. Lack of specificity of the assay for LH is probably not due simply to the endogenous secretion of this hormone. Progesterone and oestradiol-17β had no definite effect on the assay but norethynodrel significantly reduced the slope of the dose-response line. Feeding the mice with methylthiouracil increased the sensitivity to a small but significant extent. Assays depending on the induction of ovulation in immature, pregnant and mature dioestrous mice were compared. Mice of the first two types gave more sensitive and precise assays of human urinary gonadotrophin.