Ovarian aromatase activity in the domestic fowl (Gallus domesticus).

Abstract

Fowl ovarian aromatase activity was measured by an assay based on the stereospecific elimination of tritium from [1,2-3H]testosterone. The production of tritiated water was shown to provide a valid estimate of aromatase activity under the conditions used. The small yellow follicles and ovarian stroma contained 50% of the total ovarian aromatase activity. The activity in the thecal tissue from the rapidly growing follicles reached a maximum level in the fourth largest follicles (17% of the total ovarian activity) and thereafter declined to low levels in the largest follicle and first post-ovulatory follicle. No activity was detected in the granulosa tissue from the rapidly growing follicles. It is proposed that the basal levels of plasma oestrogen in hens are maintained by production in the small yellow follicles and/or ovarian stroma. The variation in plasma oestrogen during the ovulatory cycle probably arises from secretion by the rapidly growing follicles.