Activation of adenylyl cyclase by thienopyrimidine derivatives in rat testes and ovaries

Abstract

An important role in functioning of reproductive tissues is played by signaling systems that are regulated by luteinizing hormone (LH) and human chorionic gonadotropin (hCG) that include LH receptors as sensor components. Use of LH and hCG in medicine for treatment of diseases of the reproductive system and for solution of tasks of auxiliary reproductive technologies is restricted by their high cost, the necessity of parenteral introduction, and the presence of side effects. However, in the last few years, low molecular weight agonists of LH receptor have been developed that are devoid of these shortcomings and can be administered perorally. The most effective of them are thienopyrimidine derivatives, in particular the Org 43553 compound. The goal of this work was to study the effect of newly synthesized analogs of Org 43553, 5-amino-N-(tert-butyl)-4-(3-(isonicotinamide)phenyl)-2-(methylthio)thieno[2,3-d]pyrimidine-6-carboxamide (compound 1) and 5-amino-N-(tert-butyl)-2-(methylthio)-4-(3-(thiophene-3-carboxamido)phenyl)thieno[2,3-d]pyrimidine-6-carboxamide (compound 2), on the basal and LH-stimulated adenylyl cyclase (AC) activity in the plasma-membrane fractions isolated from testes and ovaries of rats. Compounds 1 and 2 have been shown to stimulate in a dose-dependent manner the basal AC activity in the membranes isolated from the testes and ovaries, compound 2 being more effective as compared with compound 1. The EC50 values for compounds 1 and 2 on AC activity were 1.05–1.12 and 0.28–0.37 μM, respectively. The stimulating effect of hCG on AC activity was retained in the presence of the thienopyrimidine derivatives, while at low, nonsaturating hormone concentrations, the additivity of the effects of hCG and of compounds 1 and 2 on the AC activity was observed. This indicates that the thienopyrimidine derivatives interact with the allosteric site located in the LH receptor transmembrane channel and does not overlap with the binding site of gonadotropins located in the N-terminal ectodomain. The action of compounds 1 and 2 was tissue-specific and not found in tissues with no LH receptors present. Our obtained data indicate that compounds 1 and 2 may become prototypes for creation of drugs that are regulators of functions of the male and female reproductive systems.