DIFFERENTIAL REGULATION OF AROMATASE AND ANDROGEN RECEPTOR IN GRANULOSA-CELLS

During follicular development, androgen acts in three distinct ways. D uring the early stage of follicular differentiation, androgen acts as an enhancer of FSH-stimulated follicular differentiation. As follicula r differentiation progresses, this effect is decreased and androgen is mainly utilized as a substrate for estrogen synthesis under increasin g stimulation of FSH and LH. These two events are mediated by androgen receptor (AR) and aromatase (P450arom), respectively. In the rat and marmoset monkey, AR and P450arom are predominantly expressed in granul osa cells, and both are developmentally regulated. The expression of A R is highest in preantral/early antral follicles and gradually decreas es as follicles mature, whereas expression of P450arom is increased as follicular differentiation progresses. We propose that differential r egulation of these two androgen-utilizing factors contributes to the s mooth transition of developing follicles from the early stage of diffe rentiation to the fully mature ovulatory status. A failure of this tra nsition due to improper androgen stimulation might result in follicula r atresia. (C) 1997 Elsevier Science Ltd.