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

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Abstract
After a single PMS (pregnant mare serum, 50 IU) injection to 25 day old rats, FSH [follicle stimulating hormone] receptor content of the ovarian tissue increased progressively for 4 days, then showed a tendency to decrease, while LH [luteinizing hormone] receptor content remained unchanged for 3 days, then gradually increased. From these facts, a radioreceptor assay system, was established, employing 3000 rpm precipitates of homogenates of the ovaries obtained 3 days after PMS injection as the receptor preparation. The Kd of the binding of the receptor preparation to rat FSH was 7.2 .times. 10-11 M. The 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 [thyrotropin] 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 [CV] and inter-assay CV were 7.5 and 13.7%, respectively, and the assay values were well correlated with those obtained by radioimmunoassay (r [correlation coefficient] = 0.988, the slope of the regression line = 1.14).