Follicular development and ovarian hormone secretion following passive immunization of ewes against inhibin or oestradiol.

Immunization against inhibin or oestradiol causes an increase in the peripheral plasma concentration of FSH. In this study we have investigated the effect of this post-immunization rise in FSH concentration on follicular development by means of real-time ultrasonography, in ewes in which an ovary and its vascular pedicle had been autotransplanted to a site in the neck. Groups of ewes on day 10 of the luteal phase of the oestrous cycle were injected with a single 10 ml i.v. bolus of plasma from normal ewes (control; n = 4), antiserum to the 1-26 peptide fragment of the N-terminus of the alpha chain of porcine inhibin (n = 5) or antiserum to oestradiol-17 beta (n = 4). The plasma concentration of FSH was unaffected by treatment in the control group but showed a significant (P < 0.001) rise following treatment in both immunized groups (inhibin-immunized 175% over 19h; oestradiol-immunized 138% over 22 h as a per cent of the original value). This rise in FSH concentration was accompanied by a significant (P < 0.001) rise in the total number of follicles > 2.0 mm per ovary in both immunized groups (inhibin-immunized 5.5 +/- 1.0 to 13.6 +/- 1.4; oestradiol-immunized 4.6 +/- 0.5 to 11.5 +/- 1.0).(ABSTRACT TRUNCATED AT 250 WORDS)