Development and characterization of a homologous radioimmunoassay for bovine follicle-stimulating hormone.

A radioimmunoassay for bovine FSH has been developed using a rabbit antiserum against highly purified bovine FSH (160 X NIH-FSH-S1) and a 125I-labelled tracer of the same preparation. The sensitivity was 0.25 ng/ml for purified bovine FSH or 25 ng/ml with reference to a crude bovine FSH (NIH-FSH-B1) standard. Purified bovine LH and TSH showed cross-reactivities of less than 1%, while their subunits and other purified protein hormones showed no significant inhibition at concentrations up to 100 ng/ml. Ovine FSH cross-reacted significantly but in a non-parallel manner; human and rat FSH cross-reacted only slightly. The concentrations of FSH (means +/- S.E.M.) in the sera of cows (n = 12), cows at oestrus (4), bulls (7) and steers (9) were measured as 25.4 +/- 4.7, 58.4 +/- 12.6, 45.7 +/- 9.5 and 120.2 +/- 36.0 ng/ml respectively. The FSH content of bovine pituitary glands varied greatly between individuals, from 2 to 25 microgram/mg tissue. The inhibition curves of pituitary and serum FSH were parallel to that of the bovine FSH standard.