Endocrine Abstracts

In utero exposure of female lambs to testosterone affects ovarian function such that ovaries contain multiple, abnormally large antral follicles. This study characterises further the follicular and cellular abnormalities underlying excessive and prolonged large antral follicle growth. Pregnant Poll Dorset ewes were injected twice weekly (30–90 days of gestation) with 100 mg of testosterone propionate in 1 ml oil, while controls received vehicle injection only. Androgenised (A) and control (C) lambs, born in April 06, were euthanased in February 07 (A: n=10, C: n=7 ewes). The largest one-two follicles were excised (A: n=15, C: n=11 follicles), their diameter measured, follicular fluid aspirated for steroid assays and granulosa cells (GC) recovered for semiquantitative real-time PCR analysis of six transcripts known to be highly expressed in GC from differentiated antral follicles. Nested one way ANOVA confirmed that A follicles were larger (A: 7.74±0.475 mm, C: 5.56±0.539 mm; P<0.001) and had higher intrafollicular progesterone (A: 25.03±4.952 ng/ml, C: 5.43±1.712 ng/ml; P<0.001). Expression of mRNA for LHCGR was upregulated (P<0.01), while expression of FSHR mRNA was downregulated (P<0.05) in GC of the largest antral follicles recovered from A ewes. No differences were detected in mRNA expression for CYP19A1, HSD3B, INHA, and INHBA encoding aromatase, 3-beta hydroxysteroid dehydrogenase, inhibin subunit α and inhibin subunit βA. In conclusion, enhanced GC LHCGR mRNA expression, increased follicular progesterone synthesis, and the prolonged growth of large antral follicles imply that their GC respond dynamically to the elevated systemic LH concentrations seen in A ewes, although, the expression of GC differentiation marker genes regulating the ability to synthesise oestradiol and inhibin is not affected. Further studies are required to determine whether GC from large antral follicles in A ewes undergo partial luteinisation in the absence of the gonadotrophin surge, thus allowing multiple smaller follicles to develop. Research supported by the MRC, BBSRC and Pfizer.