The Inverdale gene (FecX) affects ovarian development, during both foetal and adult life. There is evidence for affects on germ-cells, the follicle and the corpus luteum. In I+ewes, follicles ovulate at a small diameter with fewer granulosa cells and the resulting corpora lutea are individually smaller compared to those in control (++) animals. This appears to be due to the granulosa cells in I+ follicles being more responsive to follicle-stimulating hormone (FSH) and acquiring receptors for luteinising hormone (LH) earlier than in cells from ++ ewes. These differences between I+ and ++ ewes in ovarian characteristics occur in the absence of any obvious differences in the peripheral plasma concentrations of FSH and LH or the ovarian secretion rates of inhibin, oestradiol and progesterone. In II animals, ovarian follicular growth is impaired at the primary stage of growth during foetal, neonatal and adult life. No normal follicles beyond this stage of growth have been observed. II animals also have castrate levels of FSH and LH and undetectable plasma levels of ovarian steroid or inhibin. In ~35% of II animals, abnormal surface-visible structures have been observed with a morphology consistent with that of a sertoli-cell or sex-chord stromal tumour. These structures, which secrete inhibin, appear to develop from clusters of oocyte-free follicles.
Proceedings of the New Zealand Society of Animal Production, Volume 55, , 301-303, 1995
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