TRIIODOTHYRONINE (T3) MODULATES HCG-REGULATED PROGESTERONE SECRETION,CAMP ACCUMULATION AND DNA CONTENT IN CULTURED HUMAN LUTEINIZED GRANULOSA-CELLS

Ample clinical evidence indicates that women with thyroid disorders fr equently exhibit menstrual disturbances and impaired fertility. In ord er to characterize the nature of thyroid hormone action in the ovary, the direct effects of triidothyronine (T3) were investigated in vitro using a culture system of human luteinized granulosa cells. The presen ce of T3 receptors was also searched in such cells. The cell cultures were maintained in serum-free Ham's F-10 medium in the absence or pres ence of hCG, with or without graded doses of T3 (10(-11)-10(-7) M), an d cell proliferation (assessed by DNA content) as well as cell functio n (cAMP accumulation and progesterone secretion) determined. T3 alone stimulated cell proliferation. hCG, on the other hand, was anti-mitoge nic and T3 combined with hCG inhibited cell growth even further, reach ing levels below those reached by either control or hCG alone. Exposur e of cells to T3 markedly enhanced hCG-induced cAMP accumulation. Addi tion of 1-methyl-3-isobutylxanthine (MIX) abolished the cAMP-stimulato ry effect elicited by T3, suggesting that the thyroid hormone may act, as MIX, by inhibiting phosphodiesterase. T3 was devoid of any influen ce on basal progesterone secretion, but inhibited hCG-induced secretio n of the steroid. The effects of T3 are not accounted for by changes i n cell number since the influence of thyroid hormone on cAMP and stero id secretion were expressed per mug DNA. The action of thyroid hormone on ovarian function and growth may be receptor-mediated since saturab le, high affinity (K(D) = 4.2 +/- 0.8 x 10(-10) M), low capacity (1510 +/- 152 fmol/mg DNA) T3 binding sites were found in the nuclei of hum an luteinized granulosa cells. Optimal conditions for T3 binding to th e nuclei of such cells were determined. In conclusion, we have demonst rated that human luteinized granulosa cells contain thyroid hormone bi nding sites and that these cells serve as target to T3 action, in part icular T3 modulating hCG-mediated ovarian cell proliferation and funct ion. Our in vitro data of a direct T3 ovarian influence may account fo r the in vivo indications of a thyroid-ovarian connection.