Ovarian LH/hCG receptors and plasma level of LH,17-ß estradiol and progesterone in gonadotropin — induced PCO syndrome in rats

Summary

The aim of this work was to investigate the morphologic changes, LH/hCG receptor content in the ovaries and plasma levels of LH, progesterone and estradiol of hypo — and hyperthyroid rats injected with PMSG and hCG The hypothyroid state was induced by thyreoidectomy (Tr-X) and the hyperthyroid condition by injections of 40 µg L-thyroxine daily during 21 days (T₄). Gonadotropins were injected during 14 days in daily doses: PMSG — 5 i. u. and hCG — 10 i. u. The following 8 groups (n = 10—20) were estalished: control (euthyroid, no treatment), Tr-X, PMSG + hCG, Tr-X + hCG, Tr-X + PMSG, Tr-X + PMSG + hCG, T₄ and T₄ + PMSG. At the end of experiments rats were sacrificed, ovaries weighed, macroscopically inspected and concentration of LH/hCG receptors was estimated. In blood plasma the level of LH, progesterone and 17-ß estradiol was also analysed.

The experiments showed that injections of PMSG alone, or PMSG + hCG in eu-or hypothyroid rats, appear the most effective in induction of PCO syndrome in rats. Low levels of thyroid hormones sensitized the ovaries to gonadotropin action, but a hyperthyroid status diminished or inhibited this response.

Thyroid function is also essential in production of LH/hCG receptors in the ovaries. In hypothyroid animals the amount of these receptors was greatly increased, while in hyperthyroid animals they decreased. The level of plasma LH, progesterone, and estradiol showed insignificantly differences and various inconsiderable deviations from norm. These differences were not dependent on large doses of gonadotropins, altered thyroid function, or on cystic or luteinizing changes in the ovary.

Key words

Rats - PCO syndrome - LH/hCG receptors - plasma LH - progesterone - estradiol