Influence of follicular maturation on 3-hydroxy-methylglutaryl coenzyme A reductase activity in hen granulosa cells.
The activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase: EC 1.1.1.34) was measured in a microsomal preparation of the granulosa of rapidly growing ovarian follicles of laying hens in the late preovulatory period (2-3 h before expected ovulation). The specific activity of the enzyme was measured in the five largest (F1-F5) preovulatory follicles, F1 being the follicle destined to ovulate first. Enzyme activity increased concomitantly with follicle size. The apparent Km of the enzyme decreased 60-80% from the smallest to the largest preovulatory follicle. There was no significant change in the Vmax during follicle development. Although our results have demonstrated the presence of HMG/CoA reductase in chicken granulosa cells and the progressive increase of its activity with follicular maturation, the quantitative significance of de-novo synthesized cholesterol as steroid hormone precursor remains to be ascertained.
D000818:Animals; D002645:Chickens; D005260:Female; D005498:Follicular Phase; D006107:Granulosa Cells / Q000201:enzymology*; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism*; D025782:Hydroxymethylglutaryl-CoA-Reductases, NADP-dependent; D006080:Ovarian Follicle / Q000502:physiology*
D006903:Hydroxymethylglutaryl CoA Reductases; D025782:Hydroxymethylglutaryl-CoA-Reductases, NADP-dependent