PLASMA GONADOTROPIN CONCENTRATIONS AND OVARIAN CHARACTERISTICS IN INVERDALE EWES THAT ARE HETEROZYGOUS FOR A MAJOR GENE (FECX(1)) ON THE X-CHROMOSOME THAT INFLUENCES OVULATION RATE

Ewes heterozygous (I+) for the Inverdale prolificacy gene (FecX(I)) lo cated on the X chromosome have ovulation rates approximately 1.0 times higher than noncarriers (++). The aims of this study were to examine, in I+ and ++ ewes, the peripheral plasma concentrations and/or ovaria n secretion rates of FSH, LH, inhibin, estradiol, and progesterone dur ing anestrus and the estrous cycle and after ovariectomy. Also examine d were aspects of ovarian morphology and functions of granulosa cells in vitro. No FecX(I)-specific differences were noted for the ovarian h ormones or for FSH or LH. However, I+ animals contained significantly more ovarian antral follicles (p < 0.05) and their granulosa cells had a higher mean LH responsiveness in vitro with respect to cAMP synthes is at smaller follicular diameters relative to ++ ewes (I+ = > 2.5 mm; ++ = > 4.5 mm). Moreover, nonatretic follicles in I+ animals compared to the ++ genotype contained fewer granulosa cells and smaller CL. Al though the I+ animals had a higher ovulation rate than the controls (p < 0.05), the total weight of CL was not different between the genotyp es. These findings suggest that the FecX(I) gene affects ovarian funct ion without altering ovarian hormone secretion. The findings also sugg est that there are no FecX(I)-specific differences in the mean concent rations of gonadotropins, although further studies on temporal changes in gonadotropin secretion arc warranted.