Interspecies differences in testicular LH receptors and in vitro testosterone production among rodents

Testes from rats, mice and hamsters were incubated for 4 h with 0, 3.125 or 12.5 mIU hCG/ml. The LH receptor concentration in incubated testes of rats and mice was higher than that observed in hamsters. Testosterone levels in incubation media were significantly different among species (mice greater than rats greater than hamsters). During the incubation, hCG caused an increase in testosterone levels in all three species, but produced no significant changes in LH receptor concentration. Furthermore, a correlation between LH receptor concentration and testosterone only in hamsters is observed. The efficiency of the LH receptor-steroidogenesis interaction was estimated from the ratio of testosterone levels to receptor concentration under basal conditions and was found to differ among species (mice greater than hamster greater than rats). The levels of PGE and PGF in incubation media were higher in mice than in rats or hamsters, and hCG did not alter prostaglandin levels in any of the species. The present results indicate that acute in vitro hCG stimulation of testosterone synthesis does not involve appreciable changes in testicular LH receptor levels.