FSH bioactivity in commercial preparations of gonadotropins

During the past 2 decades, commercial preparations of FSH have been extensively used to superovulate cattle. The problems that have been encountered in superovulation of cattle include high variability in the ovulation rate and subsequent yield of viable embryos. The lack of predictability in superovulatory trials has been attributed to difficulties in standardizing the potency of commercial FSH preparations. Traditionally, FSH potency has been tested in bioassays that utilize specific responses in whole animals or primary cell cultures. Whole animal bioassays lack sensitivity, while primary cell culture bioassays, which use fresh cells, have inherent variability within each preparation. An FSH bioassay that employed a stable chimeric cell line expressing the human FSH-R was used to provide an accurate measurement of FSH bioactivity. The hormonal potency of 2 commercial preparations of FSH used to superovulate cattle was determined using FSH immuno- and bioassays. Commercial FSH preparations differed in potency. One commercial product, prepared in 4 different years, showed no difference in the immunoactive levels of FSH. In the same product stored under identical conditions, FSH bioactivity varied from year to year. There was variability in FSH bioactivity both between and within commercial products. The lack of correlation between bioactivity and immunoactivity of commercial FSH preparations may explain, in part, the variability observed in superovulation of cattle.