Decrease in the Basal and Luteinizing Hormone Receptor Agonist –Stimulated Testosterone Production in Aging Male Rats

AbstractIn the course of aging, the steroidogenic function of the testes weakens and their gonadotropin sensitivity decreases. However, the underlying mechanisms are poorly understood. The goal of this work was to study the stimulating effects of human chorionic gonadotropin (hCG) and TP03, a low molecular weight agonist of luteinizing hormone (LH)/hCG receptor, on testosterone production and the expression of steroidogenic proteins in young (3-month-old) and aging (15-month-old) male rats and to investigate the activity of the adenylyl cyclase system in the membranes isolated from the rat testes. Treatment with hCG (100  IU/rat/day) and TP03 (15 mg/kg/day) was carried out for 3 days. In the testes of aging rats, adenylyl cyclase stimulation by gonadotropin and guanine nucleotide was decreased, indicating a weakening of the coupling of LH/hCG receptor and Gs protein, the main components of the adenylyl cyclase system regulating the steroidogenesis. In elderly rats, the blood testosterone levels and the expression of theStar,Cyp11a1, andCyp17a1 genes, which encode the StAR protein and the steroidogenic enzymes cytochromes P450scc and P450-17 α in the testes, were decreased. The stimulating effect of both hCG and TP03 on testosterone production diminished with age, although their effects on LH/hCG receptor are mediated by different mechanisms. In both young and aging rats, hCG treatment upregulated the expression of the genes encoding S tAR, P450scc and dehydrogenase 3β-HSD;...
Source: Advances in Gerontology - Category: Geriatrics Source Type: research