Characterization of a radioimmunoassay for ovine FSH utilizing an anti-bovine FSH serum.

The sensitivity of the assay, utilizing a bovine FSH antiserum and 125I-labelled bovine FSH tracer, is 5 ng NIH-FSH-S6/ml, and cross-reactivities of other ovine pituitary glycoprotein and protein hormones (LH, TSH, growth hormone and prolactin) are less than 1.0%. Both pituitary and serum FSH of the sheep cross-react in a manner parallel with that of standard NIH-FSH-S6. Serum FSH concentrations in 4 ewes at various times after the onset of oestrus peaked more or less coincidently with the preovulatory increase of serum LH. The serum levels of FSH and LH did not correlate proportionally but fluctuated considerably in individuals animals. The radioimmunoassay system appears to be sensitive and specific for measuring serum concentrations of FSH in rams and ewes in different physiological states.