Treatment with progesterone affects follicular steroidogenesis in anoestrous ewes

Abstract

Ovaries were recovered from two groups ( n=6/group) of anoestrous Romney Marsh ewes, one group of which had been treated with progesterone implants prior to slaughter. A comparison was made between the maturational characteristics of the follicles > 2 mm diameter recovered from both groups and some significant differences were noted. In particular, the large follicles (> 4 mm diameter) recovered from the progesterone-treated ewes had a significantly ( P<0.01) reduced capacity to secrete oestradiol, but enhanced ( P<0.01) ability to bind hCG when compared to follicles recovered from control ewes. There were also differences in the relationships between follicular characteristics in the two groups of animals including a significant ( P <0.05) correlation between follicular fluid progesterone and hCG binding to theca tissue in large follicles from progesterone-treated animals which did not exist in the control animals. Conversely, in the control animals a significant ( P<0.05) relationship existed between oestradiol production and hCG binding to granulosa cells, but there was no such relationship in the follicles from progesterone-treated ewes. These results demonstrate that the treatment of ewes with progesterone during the anoestrous period clearly affects oestradiol synthesis and hCG binding and thus modifies follicular development.