Increase in ovulation rate after active immunization of sheep with inhibin partially purified from bovine follicular fluid

Abstract

Four Romney ewes were actively immunized with a partially purified preparation of inhibin derived from bovine follicular fluid and their ovulation rates in four successive oestrous cycles were compared with those of four ewes receiving adjuvant alone. The ovulation rates of the ewes immunized with the inhibin preparation were significantly higher than those of the control ewes (2.06 +/- 0.16 (S.E.M.) vs 1.31 +/- 0.06 ovulations/ewe, n = 4). Plasma concentrations of FSH and LH, measured in blood samples taken three times a week for 11 weeks, during which time each ewe was immunized three times, were not significantly different between the two treatment groups. These results suggest that active immunization with inhibin-enriched follicular fluid may be a potential means of increasing fecundity in sheep.

Effects of active immunization against a synthetic peptide sequence of the inhibin -subunit on plasma gonadotrophin concentrations, ovulation rate and lambing rate in ewes

“…This study confirms and extends previous reports that active immunization of sheep against inhibin-containing preparations including partially purified bovine follicular fluid (Henderson et al, 1984;O'Shea et al, 1984;Cummins et al, 1986), recombinant DNA-derived inhibin subunits (Forage et al, 1987;Tsonis et al, 1989;Mizumachi et al, 1990) and chemically synthesized frag¬ ments of inhibin (Wrathall et al, 1990) can promote substantial (2^1-fold) increases in ovulation rate. It was demonstrated that the plasma of ewes immunized against a synthetic fragment of the asubunit of inhibin contained antibodies that bound 125I-labelled native bovine inhibin (MT 32 000), such antibodies being absent in nonimmunized and carrier-protein-immunized control ewes.…”

“…As in this earlier study, no correlation was found between inhibin antibody titre and ovulation rate of individual ewes, an observation which is consistent with the report of Forage et al (1987) but contradicts the recent findings of Tsonis et al (1989). In view of the conflicting evidence about whether active immunization against inhibin actually raises FSH secretion (Henderson et al, 1984;O'Shea et ai, 1984;Cummins et ai, 1986;Al-Obaidi et al, 1987;Findlay et al, 1989;Wrathall et al, 1990), it is still not possible to state unequivocally that the increased ovulation rate observed in inhibin-immunized ewes is due to a rise in plasma FSH levels, which would be a predicted consequence of inhibin immunoneutralization. The present study, however, provides further evidence to support this explanation since plasma FSH levels were significantly higher (25%) than in control ewes after the second booster immunization, whereas plasma LH levels did not differ significantly between immunized and control ewes.…”

“…As such, it would be anticipated that immunoneutralization of endogenous circulating inhibin would lead to an increase in plasma FSH concentrations which could promote ovarian hyperstimulation, perhaps culminating in an increased ovulation rate. Experiments involving active immunization of sheep against various inhibin-containing preparations including partially purified bovine follicular fluid (Henderson et al, 1984;O'Shea et al, 1984;Cummins et al, 1986;Al-Obaidi et al, 1987), recombi¬ nant DNA-derived preparations of the inhibin a-subunit (Forage et al, 1987;Tsonis et al, 1989;Mizumachi et al, 1990) and chemically synthesized fragments of inhibin (Wrathall et ai, 1990) have provided convincing evidence to support this theory and have proved conclusively that immu¬ noneutralization of endogenous inhibin can promote a marked increase (2-4-fold) in ovulation rate. However, very little information (Tsonis et al, 1989) is available regarding the impact of inhibin immunization on other critical stages of the reproductive process (including the ability of the ewe to display oestrus, mate, conceive and géstate) and whether the observed increase in ovulation rate is actually reflected by an increase in viable litter size.…”

Effects of Active Immunization with Inhibin α Subunit on Reproductive Characteristics of Turkey Hens1

“…Active immunization against INH neutralizes endogenous INH and increases the ovulation rate in mammals [6,7,10,[37][38][39]. The results of the present study showed no significant difference in egg production between birds that were actively immunized against INH and control hens, even though immunization significantly increased the number of preovulatory yellow follicles and significantly increased FSH␤ subunit mRNA content in the anterior pituitary.…”

“…This may be explained by the paracrine effect of INH on follicular maturation, as direct injection of rhINH A into immature rat ovaries enhances follicle maturation, which is indicated by follicular size [40]. It still remains to be proven that the ovarian response to rtINH␣ immunization is precipitated by a rise in FSH secretion (no FSH assay is available that measures circulating turkey FSH), because several studies have found plasma FSH to be unaffected by immunization despite an increased ovulation rate [9,37,39]. Immunization of hens in their first reproductive cycle with rtINH␣ increased (7.6-fold) FSH␤ subunit mRNA content more than it did in second-reproductive-cycle hens (twofold).…”