Plasma FSH, LH and immunoreactive inhibin concentrations in FecBB/FecBB and FecB+/FecB+ Booroola ewes and rams from birth to 12 months of age.

Endocrine and developmental changes were examined in Booroola FecBB/FecBB (BB, n = 16) and FecB+/FecB+ (++, n = 20) ewe lambs, and BB (n = 17) and ++ (n = 19) ram lambs from 2 to 53 weeks of age. Blood samples were taken weekly for the measurement of plasma concentrations of FSH, LH, immunoreactive inhibin, progesterone (ewe lambs) and testosterone (ram lambs). Behavioural oestrus in the ewe lambs and testicular volume and the breakdown of foreskin adhesions in ram lambs were recorded. Blood samples were taken from another flock of BB (n = 134) and ++ (n = 109) ram lambs at 20 weeks of age for the analysis of immunoreactive inhibin. In ewe and ram lambs, there appeared to be genotype differences for FSH, LH and immunoreactive inhibin at specific times during the neonatal period. In BB and ++ ewe lambs, respectively, mean FSH concentrations were 4.3 and 2.0 ng ml-1 (SED 0.54) between 4 and 6 weeks, 2.6 and 3.4 ng ml-1 (SED 0.33) between 12 and 28 weeks, and 1.8 and 1.9 ng ml-1 (SED 0.18) between 34 and 53 weeks of age. Mean plasma LH concentrations were lower in BB than in ++ ewe lambs from 26 to 53 weeks of age (P < 0.05) but not earlier. Mean concentrations of immunoreactive inhibin were also lower in BB than in ++ ewe lambs between 2 and 11 weeks (16.0 and 27.4 iu ml-1, respectively; P < 0.01), but thereafter no differences were apparent.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of the Booroola gene (FecB) on body weight, ovarian development and hormone concentrations during fetal life.

The aim of this study was to determine whether the FecB gene influenced some aspects of fetal development in sheep. Carrier (BB/B+) and non-carrier (++) female fetuses were recovered at specific times of gestation, namely, days 40, 55, 75, 90, 95 and 135. The results showed that the FecB gene influenced litter size, body weight and ovarian development during fetal life. The mean litter sizes were larger (P < 0.05) and body weights were lighter (P < 0.05) at most gestational ages in BB/B+ than in ++ fetuses. Morphometric studies of the ovary showed that the development of the BB/B+ ovaries was retarded: the ++ genotype had more oogonia at day 40 (P < 0.01), more germ cells entering meiosis at day 55, more primordial follicles developing at days 75, 90 and 95 (P < 0.05), a greater loss of germ cells by atresia at day 90 (P < 0.01) and more growing follicles (P < 0.01) and more antral follicles (P < 0.05) at day 135. Differences between the BB/B+ and ++ genotypes in the plasma concentrations of immunoreactive (i) inhibin, i-FSH, bioactive (b)-FSH or (i)-LH were not apparent at any age except for i-LH at day 75 (BB/B+ > ++; P < 0.05). Likewise no differences were noted in the contents of ovarian or adrenal oestradiol or i-inhibin except for i-inhibin in the adrenal at day 75 (++ > BB/B+, P < 0.01). No differences between the genotypes were noted in the i-inhibin contents of the mesonephros at day 40. In mid- to late but not early gestation (i.e. days 40 and 55) significant correlations (i.e. P < 0.05) were noted between litter size and body weight at days 75, 90 and 135, and between litter size and ovary weight, ovary volume, adrenal weight and pituitary weight at day 135. To eliminate the effect of litter size, equal numbers of BB/B+ and ++ embryos were transferred to respective recipient ewes, and fetuses were recovered at the equivalent of days 40 and 90 of gestation. The results showed that the genotypic difference in fetal body weight at day 40 (++ > BB, P < 0.001) and in number of oogonia at day 90 (++ > BB/B+, P < 0.05) were independent of litter size.(ABSTRACT TRUNCATED AT 250 WORDS)

Gonadotrophin-releasing hormone and the control of ovulation rate by the FecB gene in Booroola ewes.

Booroola sheep carry a FecB gene that confers high fecundity. The aims of the present studies were to determine in homozygous carriers (BB) and non-carriers (++) of the Booroola FecB gene whether there are FecB differences in the secretory characteristics of GnRH in hypophyseal-portal blood of ovariectomized ewes (Expt 1) and whether differences in ovulation rate would occur following the administration of PMSG and pulsatile GnRH to ovary-intact Booroola ewes with hypothalamic-pituitary disconnection (HPD) (Expt 2). In Expt 1, no FecB gene-specific differences were noted for GnRH with respect to pulse frequency, pulse amplitude or overall secretion rate. Irrespective of genotype there were 1.9 +/- 0.2 GnRH pulses h-1 (n = 20 ewes; 10 BB and 10 ++ animals) and 1.9 +/- 0.1 pulses of immunoreactive (i) LH h-1. In Expt 2, ovulation was induced in the HPD ovary-intact animals on three occasions (e.g. 56, 393 and 423 days after HPD surgery) using a PMSG (200 or 400 iu)-GnRH pulse (250 ng i.v. for 96 h)-GnRH bolus (10 micrograms i.v.) regimen after pretreating the animals with GnRH pulses (250 ng i.v. for 14 days). On all occasions the ovulation rates were significantly higher (P < 0.05) in BB ewes (n = 6 or 7) than in ++ animals (n = 7). No differences between the genotypes were noted with respect to the mean concentrations of progesterone in plasma notwithstanding the differences in ovulation rates.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma gonadotropin concentrations and ovarian characteristics in Inverdale ewes that are heterozygous for a major gene (FecX1) on the X chromosome that influences ovulation rate.

Ewes heterozygous (I+) for the Inverdale prolificacy gene (FecX1) located 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 ovarian secretion rates of FSH, LH, inhibin, estradiol, and progesterone during anestrus and the estrous cycle and after ovariectomy. Also examined were aspects of ovarian morphology and functions of granulosa cells in vitro. No FecX1-specific differences were noted for the ovarian hormones 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 synthesis 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. Although the I+ animals had a higher ovulation rate than the controls (p < 0.05), the total weight of CL was not different between the genotypes. These findings suggest that the FecX1 gene affects ovarian function without altering ovarian hormone secretion. The findings also suggest that there are no FecX1-specific differences in the mean concentrations of gonadotropins, although further studies on temporal changes in gonadotropin secretion are warranted.

Biopotency in vitro and metabolic clearance rates of five pituitary preparations of follicle stimulating hormone.

Five pituitary preparations of follicle stimulating hormone (FSH), namely NIDDK-oFSH-17, Bioscan oFSH, Ovagen, Folltropin-V and F.S.H.-P., were examined for biological activity in terms of their potency in an in vitro bioassay, receptor assay and heterologous radioimmunoassay and in terms of their metabolic clearance rates. In the three assays, Bioscan oFSH was the most potent (P < 0.05) (3- to 5-fold the potency of NIDDK-oFSH-17), with Ovagen being 25-50% the potency of the NIDDK standard (P < 0.05). Folltropin-V and F.S.H.-P. had the lowest potencies in all three assays. For each preparation, the ratio of activities between the assays was not consistent, suggesting that the preparations behaved differently in each assay. In 9 of 10 cases, potency estimates in the heterologous radioimmunoassay were greater than those in the in vitro bioassay or receptor assay. Polyacrylamide gel electrophoresis of the preparations showed banding consistent with the molecular weight of FSH, but also indicated that the preparations were contaminated with other proteins to varying extents. The half-lives of these preparations when injected into the bloodstream of mature female mice were 28.0, 8.6, 13.4, 11.6 and 17.4 min for NIDDK-oFSH-17, Bioscan oFSH, Ovagen, Folltropin-V and F.S.H.-P. respectively. The slopes of the decay rates were significantly different from each other (P < 0.05) except between Ovagen and Folltropin-V. The results of these studies show that a number of widely available FSH preparations have differing biopotencies. Moreover, the biopotency of a preparation in vitro is not related to its metabolic clearance rate, and not all FSH preparations behave identically in different assays. Measures of biopotency in vitro combined with those of metabolic clearance rate may provide useful information on the properties of FSH preparations used for research purposes and for superovulation of farmed livestock.

Bioactive and immunoreactive FSH and immunoreactive inhibin concentrations in the ovine fetus.

The bioactive (B) and immunoreactive (I) pituitary contents/concentrations of FSH, together with the plasma concentrations of B-FSH, I-FSH and I-inhibin were determined in ovine fetuses at days 55, 75, 90 and 135 of gestation (day 145 = term). The pituitary contents and concentrations of B-FSH and I-FSH increased in both sexes with gestational age. The female fetuses had significantly (P < 0.01) higher pituitary contents/concentrations of B-FSH and I-FSH than the male fetuses at days 75 and 135. The pituitary B/I ratios of FSH were not significantly different with age or sex. The plasma concentrations of B-FSH remained relatively constant from days 75 to 135, with no significant differences between sexes or with age. In contrast, the plasma concentrations of I-FSH reached a peak at day 90 and then declined towards term in both sexes. At all gestational ages except day 55, the female fetuses had significantly (P < 0.05) higher plasma concentrations of I-FSH than the males. In both sexes, the plasma B/I ratios of FSH were lowest at day 90 and had increased again by day 135, with the male fetuses having significantly (P < 0.05) higher B/I ratios compared with the female group at days 75 and 135 but not at day 90. At all gestational ages, the plasma concentrations of I-inhibin declined throughout gestation in the female fetuses, whereas in the males they reached a nadir at day 75 and then increased towards term. The concentrations of I-inhibin were significantly (P < 0.01) higher in the male fetuses compared with the females.(ABSTRACT TRUNCATED AT 250 WORDS)

Concentrations of immunoreactive inhibin in ovarian and peripheral venous plasma and follicular fluid of Booroola ewes that are homozygous carriers or non-carriers of the FecB gene.

No gene-specific differences were found during either the luteal or follicular phases of the oestrous cycle in the venous secretion rates of ovaries or in concentrations of immunoreactive inhibin in peripheral plasma between Booroola ewes that were homozygous carriers (BB) or non-carriers (++) of the FecB gene. In three experiments in which concentrations of plasma inhibin and follicle-stimulating hormone (FSH) were compared, gene-specific differences were noted for FSH (P less than 0.05), but no significant correlations were noted between FSH and inhibin for either genotype. Granulosa cells and follicular fluid, but not theca interna, stroma or corpora lutea, were the major intra-ovarian sites of inhibin; no gene-specific differences were noted for inhibin concentrations in follicular fluid or in any of the intra-ovarian tissues. The mean concentrations of inhibin in follicular fluid remained constant irrespective of follicular diameter whereas the mean total contents of inhibin increased significantly with increasing diameter (P less than 0.05). Inhibin secretion rates were four times higher in ovaries with oestrogen-enriched follicles (i.e. greater than or equal to 50 ng oestradiol ml-1) than in ovaries with no such follicles (P less than 0.01). Moreover, inhibin concentrations were higher in follicular fluid of oestrogen-enriched follicles than in those with low oestrogen (i.e. less than 50 ng ml-1; P less than 0.05). Ovariectomy resulted in a significant reduction in concentrations of immunoreactive inhibin from plasma (P less than 0.01). The residual plasma inhibin in some Booroola ewes was not associated with genotype. It is concluded that, although antral follicles are a major source of inhibin in Booroola ewes, immunoreactive inhibin is not associated with the FecB gene and is not responsible for the gene-specific differences in concentrations of FSH in plasma.

GnRH-induced gonadotrophin secretion in ovariectomized Booroola ewes with hypothalamic-pituitary disconnection.

To test whether the F gene-specific differences in the plasma concentrations of FSH and LH are due to differences in the pituitary responsiveness to exogenous GnRH, ovariectomized Booroola ewes with hypothalamic-pituitary disconnection (HPD-ovx) were treated with GnRH (250 ng i.v.) once every 2 h for up to 5 weeks. In Exp. 1, jugular venous blood was collected once weekly from 13 FF and 14 ++ HPD-ovx ewes for 6 weeks before GnRH treatment and every 2nd, 3rd or 6th day for 5 weeks during treatment. In Exp. 2, jugular venous blood was collected from another 8 FF and 7 ++ HPD-ovx ewes at 5- or 10-min intervals over 4 GnRH pulses (250 ng i.v. once every 2 h) on 3 separate occasions after the animals had been subjected to the GnRH pulse regimen for approximately 7 days beforehand. Also in Exp. 2, the animals were extensively sampled around a larger (10 micrograms) i.v. injection of GnRH and the pituitary FSH and LH contents assessed after the animals had been re-exposed to the once every 2 h GnRH (250 ng i.v.) pulse regimen for several days following the larger GnRH bolus. In Exp. 3 the distributions of mean plasma concentrations of FSH and LH in individual GnRH-treated HPD-ovx ewes were compared with those in ovariectomized and ovary-intact FF and ++ ewes. During the 6 weeks before GnRH treatment (Exp. 1), the plasma concentrations of FSH (approximately 1 ng/ml) and LH (less than or equal to 0.8 ng/ml) were not different between the genotypes. After GnRH treatment both the mean FSH and LH concentrations increased significantly (P less than 0.01) above basal values after 2 days with F gene-specific differences being noted for FSH but not LH (FSH; FF greater than ++; P less than 0.05). Thereafter, the mean FSH but not LH concentrations increased at a faster rate in FF than in ++ ewes with the overall mean FSH concentrations between the genotypes being significantly different (P less than 0.05). In Exp. 2 considerable between-animal variation in the pulsatile pattern of FSH but not LH concentrations was seen in ewes of both genotypes during GnRH treatment. The overall mean FSH concentrations were higher in FF than in ++ ewes (P less than 0.05) and the mean FSH response to each GnRH pulse was significantly higher in FF than in ++ ewes (P less than 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)