Effects of ovariectomy and genotype on bioactive FSH in plasma and pituitary of Booroola ewes

Abstract

Blood samples were collected for 13 days before and 20 days after ovariectomy from carrier (BB) and non-carrier (+ +) ewes of the Booroola FecB gene (n = 12 per genotype), at known stages of the oestrous cycle, after which the pituitary glands from these ewes were recovered. Pituitary glands were also collected from cyclic ewes (about day 12; n = 5 per genotype) to compare the effects of ovariectomy on pituitary gonadotrophins. Plasma samples and pituitary extracts were assayed for bioactive (B) FSH, immunoreactive (I) FSH and I-LH. Overall, BB ewes had significantly (P < 0.05) higher plasma I-FSH concentrations than did + + ewes before ovariectomy; the mean value was higher on 16 of the 17 days of the oestrous cycle (P < 0.01). For B-FSH, there were no overall genotypic differences, although the mean for the BB ewes was significantly higher on 13 of the 17 days of the oestrous cycle (P < 0.05), and significantly (P < 0.05) higher between days 13 and 16. No genotypic differences were noted for the plasma bioactive:immunoreactive (B:I) ratio for FSH before ovariectomy. After ovariectomy, there were significant (P < 0.001) increases in plasma for B-FSH, I-FSH and I-LH and a significant (P < 0.05) decrease in the B:I ratio for FSH, irrespective of genotype.(ABSTRACT TRUNCATED AT 250 WORDS)