Gonadotrophin induced development of the "special zone" in the adrenal cortex of immature female possums (Trichosurus vulpecula) with concomitant activation of steroid reductases.

The effect of gonadotrophin and oestradiol administration on adrenocortical special zone (S.Z.) development and steroidogenesis was studied in immature female possums. Adrenals were examined histologically to determine S.Z. formation, and cell-free homogenates were incubated with 3H progesterone in the presence of an NADPH-generating system. Treatment with PMS + hCG, resulted in the development of S.Z.s. varying in volume from 10 to 60% of the total adrenal gland. This response was independent of ovarian status (i.e. immature or multifollicular). Treatment with porcine FSH (NIH-FSH-P2) also induced development of a S.Z. Oestradiol treatment was ineffective. The appearance of the S.Z. was associated with a change in steroidogenesis. The adrenals of controls produced cortisol and corticosterone in yields of approx. 70%, while these products were less than 22% in the animals with S.Z.s. The major conversion products in the treated animals were 5 beta-reduced pregnane derivatives, in yields ranging from 67 to 93%. The yields of products from the oestradiol treated animals closely resembled those of the controls. It was concluded that FSH is capable of inducing the development of an adrenocortical S.Z. in immature female possums and consequently stimulating adrenal steroid reduction. It appeared that oestradiol was not involved in this process.