Influence of mesonephros on foetal and neonatal rabbit gonads. II. Sex-steroid release by the ovary in vitro.

To test whether the mesonephros influences the steroid hormone release by the foetal and neonatal ovary, rabbit ovaries were cultured with and without the mesonephros for a period of 5 days. The media were harvested once every day and analyzed by RIA for the content of testosterone, oestradiol and progesterone. Mesonephros produced progesterone only at day 20 pc. At day 21 and 28 pc significant amounts of all three hormones were produced. The media of the co-cultures of ovaries with the mesonephros contained on day 23 and 28 pc less testosterone. On day 23 pc less les and on day 3 pp more oestradiol was found in the media of the co-cultures. At day 21 pc progesterone release was increased by the mesonephros. It could be concluded that the mesonephros is able to synthetize steroids and possesses the capacity both to lower and to increase ovarian steroid release in culture. The enhancement of ovarian steroid synthesis in cocultures with the mesonephros at certain ages might be due either to increased substrate production and/or increased enzymatic activity. The lowering of steroids seen at different ages might be due to mesonephric steroid binding. The mesonephros appeared to influence the male and female rabbits differently at the same ages.