DYNAMICS OF THE STIMULATING EFFECTS OF GONADOTROPIN AND THIENOPYRIMIDINE DERIVATIVE TP03 ON OVULATION AND OVARIAN STEROIDOGENESIS IN FOLLIMAG-STIMULATED IMMATURE FEMALE RATS

Gonadotropin preparations, primarily human chorionic gonadotropin (hCG), are widely used to induce ovulation and correct reproductive disorders in women, but they are characterized by a number of side effects. A possible alternative is low-molecular-weight allosteric agonists of the luteinizing hormone receptor (LHR), including the thieno[2,3-d]-pyrimidine derivatives we developed. The purpose of the work was a comparative study of the effect of thieno[2,3-d]-pyrimidine TP03 and hCG on ovarian weight, corpus luteum formation, plasma levels of estradiol, progesterone and LH in immature female rats pre-treated with Follimag, as well as their effect on expression of ovarian genes encoding LHR and key components of steroidogenesis. TP03 was administered at a dose of 20 mg/kg (i.p.), hCG at a dose of 15 IU/rat (s.c.), both 48 hours after the Follimag injection. The estimated parameters were studied 1, 2, 4, 8, 16 and 24 hours after administration of TP03 or hCG. Plasma levels of hormones were determined using ELISA, and gene expression in the ovaries was determined using real-time PCR. The allosteric LHR agonist TP03 increased ovarian weight, progesterone production in the blood and the expression of steroidogenic genes encoding the cholesterol-transporting protein StAR and the cytochromes CYP11A1 and CYP17A1, and also stimulated the formation of the corpus luteum (1624 hours after treatment). The temporal dynamics of its stimulating effects were similar to those of hCG, although their magnitude was slightly inferior to those of gonadotropin. The TP03-induced decrease in blood estradiol levels and aromatase gene expression in the ovaries was also more moderate. Unlike hCG, which suppressed the expression of the gene encoding LHR 8 hours after treatment, TP03 maintained a high level of expression of this gene, preventing a decrease in the sensitivity of the ovaries to endogenous LH. Thus, TP03 is a good candidate for the role of an ovulation inducer, acting more mildly than hCG in terms of stimulating ovarian steroidogenesis, which reduces the risks of developing ovarian hyperstimulation syndrome and resistance of ovarian cells to gonadotropins.