Adenosine 3',5-cyclic monophosphate phosphodiesterase activity in granulosa cells from Booroola x Romney ewes with and without the F gene

Granulosa cells from ovarian follicles (greater than or equal to 1 mm diameter) in Booroola ewes which are homozygous (FF) or heterozygous (F+) for the F gene have previously been shown to produce significantly more cAMP in response to FSH or LH than those from similar sized follicles in ewes without the F gene (++). The aim of these studies was to test whether these F gene-specific differences arose because of differences in cAMP-phosphodiesterase (cAMP-PDE) activity. In the first study using 1 mumol cAMP/l as substrate, no F gene-specific effects were noted in cAMP-PDE activity in granulosa cells from small (1-2.5 mm diameter, n = 4 per genotype) or large (greater than or equal to 3 mm diameter, n = 4 per genotype) follicles from FF, F+ or ++ ewes, despite F gene-specific effects in FSH (1 microgram/ml)- and LH (0.1 microgram/ml)-induced cAMP accumulation in these same cell preparations. The overall mean levels of cAMP-PDE across all genotypes in cells from small and large follicles were 0.47 +/- 0.04 (S.E.M., n = 12) and 0.28 +/- 0.03 pmol cAMP/10(6) cells per min respectively; the mean PDE activity in cells from small follicles was significantly (P less than 0.05) higher compared with that in cells from large follicles. In a second study, granulosa cells from each genotype were pooled over all follicle sizes (greater than or equal to 1 mm diameter, one pool per genotype) and the rates of cAMP hydrolysis tested over a range of substrate concentrations (0-16 mumol/l) but no gene-specific differences with respect to the Michaelis constant and maximum velocity were noted.(ABSTRACT TRUNCATED AT 250 WORDS)