A simple in vivo bioassay for inhibin-like activity using ovariectomized ewes

Long term ovariectomized ewes were used in a bioassay for inhibin-like activity. The concentration of FSH 6 to 7 hr after injection of follicular fluid (a rich source of inhibin), as a percentage of pretreatment, regressed on the log of the dose had a slope of -26.0 +/- 7.6 (5 replications, mean +/- SD) and an index of precision of .32 +/- .04. This system was rapid, relatively easy and specific for in vivo inhibin-like activity. This bioassay was also used to determine the relative potency of an affinity-purified fraction of follicular fluid.