title: In Vitro Effect of Triiodothyronine on the Cyclic AMP, Progesterone and Testosterone Level in Porcine Theca, Granulosa and Luteal Cells.
abstract: OBJECTIVE: To investigate the influence of thyroid hormone on steroid production and cAMP accumulation in porcine theca (Tc) and granulosa cells (Gc) isolated from preovulatory follicles as well as in luteal cells isolated during the mid-developing luteal phase. METHODS: Granulosa and theca cells separated from pig ovarian follicles and pieces of corpora lutea were cultured in the incubation medium M199 with 5 % calf serum. After the addition of triiodothyronine (T3) and 3-isobutyl-1-methyl xanthine (IBMX) to the culture medium cAMP, progesterone and testosterone were estimated with the aid of specific RIA. RESULTS: T3 added to the culture media stimulated the steroid secretion and cAMP accumulation in all cell types investigated. In theca cells, T3 alone increased androgen production by 2 fold and the addition of IBMX further augmented the steroidogenesis by 2.2 fold. In granulosa cell culture, IBMX had no effect either on the basal or T3 stimulated progesterone secretion and cAMP accumulation. In luteal cell culture, IBMX added alone increased progesterone secretion and cAMP accumulation in the same manner as T3. Further augmentation of progesterone secretion (1.3-fold) and cAMP accumulation (1.1-fold) was observed after the addition of IBMX together with T3. CONCLUSION: The influence of thyroid hormone on cyclic nucleotide release by ovarian cells may suggest the involvement of cAMP-dependent mechanism in the realisation of T3 action in ovarian cells.