A sensitive radioreceptor assay for follicle stimulating hormone with PMS-primed immature rat ovary.

After a single PMS (50 IU) injection to 25-day-old rats, FSH receptor content of the ovarian tissue increased progressively for 4 days, then showed a tendency to decrease, while LH receptor content remained unchanged for 3 days, then gradually increased. From these facts, we established a radioreceptor assay system, employing 3,000 rpm precipitates of homogenates of the ovaries obtained 3 days after PMS injection as the receptor preparation. The dissociahe standard curve was obtained with 0.125--16 ng/tube of NIAMDD rat FSH I-3. Purified preparations, NIAMDD rat LH I-4 and NIAMDD rat TSH I-4 influenced the binding only at high concentrations possibly owing to FSH contamination. When the anterior pituitary homogenates obtained from rats in the various physiological states were assayed by this system, the intra-assay coefficient of variation and inter-assay coefficient of variation were 7.5% and 13.7%, respectively, and the assay values were well correlated with those obtained by radioimmunoassay (r = 0.988, the slope of the regression line = 1.14).