Ed. Watson et Srm. Thomson, IMMUNOLOCALIZATION OF AROMATASE P-450 IN OVARIAN TISSUE FROM PREGNANTAND NONPREGNANT MARES AND IN OVARIAN-TUMORS, Journal of Reproduction and Fertility, 108(2), 1996, pp. 239-244
Aromatase P-450 (P-450(arom)) is a crucial regulatory enzyme that is n
ecessary for conversion of androgens to oestrogens. Corpora lutea and
follicles were obtained from the ovaries of cyclic mares and from mare
s at day 20 and days 40-70 of pregnancy. The presence of P-450(arom) w
ithin specific cell types was investigated by immunostaining to determ
ine potential sites of oestrogen synthesis. Immunoreactivity for P-450
(arom) was confined to the granulosa layer of non-atretic follicles >
5 mm in diameter and to corpora lutea at all stages of the oestrous cy
cle and during pregnancy. These findings confirm that aromatization of
androgens occurs within the granulosa cells of the preovulatory folli
cle of the mare and that the corpus luteum of the mare has the capacit
y for oestrogen production if adequate androgen substrate is available
. Granulosa cells in ovarian tissue from three mares with granulosa ce
ll tumours showed little staining for P-450(arom), which suggests that
these rumours have little aromatizing capacity.