Increase in ovulation rate in Merino ewes after active immunization with inhibin preparations obtained by immunoaffinity chromatography

Abstract

Ewes were immunized with four inhibin preparations of increasing purity obtained from bovine follicular fluid by affinity chromatography. The two purest immunogens, which had 69 and 174 ng inhibin micrograms-1 protein (expressed in terms of 32 kDa ovine inhibin), increased ovulation rate by 240 and 320% respectively following two injections, and gave a transient increase in plasma FSH concentration at the same time. Plasma antibodies recognizing native 125I-31 kDa bovine inhibin appeared at the same time, and, together with the increased ovulation rate, persisted after the injections ceased. Ovulation rate and antibody titres were raised by the less pure immunogens, but to a smaller extent, and the increases did not persist. It was concluded that the increased ovulation rate was due to induced inhibin antibodies, acting at least in part through the consequent rise in plasma FSH concentration.