Differences in gonadotrophin-stimulated cyclic AMP production by granulosa cells from Booroola x Merino ewes which were homozygous, heterozygous or non-carriers of a fecundity gene influencing their ovulation rate

Abstract

Granulosa cells from follicles of different sizes from Booroola x Merino ewes which were homozygous (FF), heterozygous (F+) or non-carriers(++) of a fecundity gene were obtained 0-48 h after cloprostenol injection on Day 10 of the oestrous cycle. The highest mean amounts of cAMP produced by the cells did not differ between the genotypes. However, in the ++ ewes it was attained by cells from follicles greater than or equal to 5 mm in diameter, whereas in F+ and FF ewes it was attained by cells from follicles 3-4.5 mm in diameter. Cells from 1-2.5-mm diameter follicles of FF ewes were more sensitive to FSH and LH than were corresponding cells from F+ or ++ ewes. Granulosa cells from greater than or equal to 5 mm diameter follicles of ++ ewes 12-24 h after injection of cloprostenol had a lower mean response to FSH and LH than did cells obtained 0-6 or 36-48 h after cloprostenol. No such effect of time was evident for cells from any size of follicles obtained from F+ or FF ewes. In 1-2.5-mm diameter follicles, the mean aromatase activity of granulosa cells from ++ and F+ ewes was similar, but significantly lower than that of cells from FF ewes. In 3-4.5 mm diameter follicles, the mean aromatase activity of cells from F+ and FF ewes was similar, and significantly higher than that of cells from ++ ewes. For all 3 genotypes, there was a significant positive relationship between FSH or LH stimulation of granulosa cell cAMP production and cellular aromatase activity.

Oocytes in sheep homozygous for a mutation in bone morphogenetic protein receptor 1B express lower mRNA levels of bone morphogenetic protein 15 but not growth differentiation factor 9

“…The cAMP responses induced by FSH were influenced by follicular diameter and dose of FSH, which is consistent with our earlier observations (Henderson et al 1987). Previously, we also reported a genotype difference in the sensitivity of GC to FSH as well as LH (Henderson et al 1987). However, we now know that the FSH preparation was contaminated with w1-2% LH (McNatty et al 2009).…”

“…A reduction in mRNA levels of these growth factors in atretic follicles is likely to be due to the reduced support to the oocyte through the loss of cell-to-cell contacts between the GC, and between the GC and the oocyte (Wiesen & Midgley 1994, Lenhart et al 1998, Carabatsos et al 2000. The cAMP responses induced by FSH were influenced by follicular diameter and dose of FSH, which is consistent with our earlier observations (Henderson et al 1987). Previously, we also reported a genotype difference in the sensitivity of GC to FSH as well as LH (Henderson et al 1987).…”

“…O4.5 mm), with the ovulating follicles in BB ewes each containing fewer GC (McNatty et al 1986, Henderson et al 1987. Moreover, similar to that which occurs in Inverdale ewes, GC in BB ewes develop a responsiveness to LH earlier in follicular development, consistent with the reduced size of the ovulating follicles (Henderson et al 1987). It should be noted that although the GC in small (i.e.…”

“…!0.002%) and there was no genotype effect of FSH on cAMP production. Thus, as with heterozygous BMP15-mutant Inverdale ewes (McNatty et al 2009), the early maturation of antral follicles observed in BB ewes is unlikely to be due to a greater sensitivity to FSH, as known previously (Henderson et al 1987).…”

“…It should be noted that although the GC in small (i.e. 1-2.5 mm) antral follicles of BB ewes also showed an increased sensitivity to FSH with respect to cAMP production (Henderson et al 1987), the FSH preparations used in this experiment contained O1% contamination of LH (McNatty et al 2009). …”