Dynamics of gonadotropin and thienopyrimidine derivative TP03 effects on ovulation and ovarian steroidogenesis in Follimag-stimulated immature female rats

Abstract

BACKGROUND: Gonadotropin preparations, particularly human chorionic gonadotropin (hCG), are commonly used to induce ovulation and treat reproductive disorders in women, albeit with associated side effects. Low-molecular-weight allosteric agonists of the luteinizing hormone receptor (LHR), such as thieno[2,3-d]pyrimidine derivatives, offer a potential alternative. AIM: This study aims to compare the effects of thieno[2,3-d]pyrimidine TP03 and hCG on ovarian weight, corpus luteum formation, and plasma levels of estradiol, progesterone, and luteinizing hormone in immature female rats pre-treated with Follimag®. It also examines their impact on ovarian gene expression related to LHR and steroidogenesis. MATERIALS AND METHODS: TP03 and hCG were administered 48 h after the Follimag® injection at a dose of 20 mg/kg (i.p.) and 15 IU/rat (s.c.), respectively. Parameters were assessed at 1, 2, 4, 8, 16, and 24 h after TP03 and hCG administration. Plasma hormone levels were measured via ELISA, and ovarian gene expression was analyzed using real-time PCR. RESULTS: TP03 increased ovarian weight, progesterone levels in the blood, and expression of steroidogenic genes encoding the cholesterol-transporting protein StAR and the cytochromes CYP11A1 and CYP17A1. TP03 also stimulated corpus luteum formation (16–24 h 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. TP03-induced decrease in blood estradiol levels and aromatase gene expression in the ovaries was also more moderate. Unlike hCG, which suppressed LHR gene expression 8 h after treatment, TP03 maintained a high LHR gene expression, preserving ovarian sensitivity to endogenous luteinizing hormone. CONCLUSIONS: TP03 exhibits potential as an ovulation inducer with milder stimulating effects on ovarian steroidogenesis than hCG, which reduces the risks of developing ovarian hyperstimulation syndrome and resistance to gonadotropins.