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Ovarian function in the ewe after active immunization against testosterone

Summary. The secretion rates of testosterone measured during the last half of the oestrous cycle in 2 Merino crossbred ewes with utero-ovarian autotransplants were 1·95 ± 0·34 ng/min and 2-48 0-63 ng/min. The secretion rate of testosterone was not correlated with the secretion rate of oestradiol or androstenedione in either ewe.

Welsh Mountain ewes were actively immunized against testosterone-3-(0carboxymethyl)-oxime-bovine serum albumin (testosterone-3-BSA) or BSA alone (controls). Immunization against testosterone-3-BSA (5 ewes) resulted in anovulation (2 ewes) and the disruption of oestrous cycles and irregular ovulations (2 ewes). The ovaries showed morphological and endocrinological evidence of over-stimulation. Numerous large non-atretic follicles were present and in those ewes still ovulating the numbers of corpora lutea (ovulation rate) were increased. The concentrations of androstenedione and of oestradiol in the ovarian venous plasma were also markedly increased when compared to those in control ewes. The plasma binding capacity for steroids and the jugular venous concentrations of steroids were higher in immunized ewes. The binding capacity of follicular fluid for testosterone was similar to that of jugular venous plasma from the same ewe.

These results show that immunization against testosterone-3-BSA leads to a disruption of ovarian cycles and ovarian over-stimulation.