PARENT SESSION

(M424) IS CONNEXIN43 REQUIRED FOR TESTICULAR STEROIDOGENIC FUNCTIONS?

Kahiri, Caroline ¹, Tekpetey, Francis ¹, Khalil , Wahid¹, Kidder, Gerald¹, ¹ University of Western Ontario, London, ON, Canada

ABSTRACT- The physiological relevance of the gap junction protein, connexin43 (Cx43) for spermatogenesis is underlined by the effects of deleting the encoding gene, Gja1. In Cx43 knockout mice, the gonads show a severe deficiency of germ cells but it has not been established if this is due to altered steroid support from the Leydig cells. Therefore, testicular androgen production and regulation were studied in mice lacking Cx43. Testes from wild type or mutant term fetuses were grafted under the kidney capsules of wildtype adult males, allowing post-partum development. To determine the hormonal output from the grafted testes, the host's testes were removed in one experimental group. It was hypothesized that Cx43 deficiency would alter androgen production by the Leydig cells. Serum from host mice was analyzed for androgens and gonadotropins, and intratesticular testosterone was measured from the mutant and control testes. To test their response to stimulation, the grafted testes were incubated in vitro with varying concentrations of LH and their androgen end products analyzed. HPLC separation was used in determination of the testosterone intermediate metabolites, and the activity of testosterone metabolizing enzymes in the grafted testes. Dye transfer was used to test cell communication between the Leydig cells. Host mice carrying Cx43 deficient or wildtype testes did not differ in serum androgen or gonadotropin levels. Furthermore, sensitivity to LH stimulation in vitro was not affected by lack of Cx43. However, there was an increase in intratesticular androgens that reflected higher enzyme activity observed in the mutant testes. Since the mutant testes are much smaller than the wild type testes, the enzyme activity in the mutant makes their output comparable to that of wild type testes. In addition the androgen contribution from each grafted testis was minimal, hence an overall change in host circulation was lacking. Thus Cx43 deficiency does not impair androgen production by the testes. Correspondingly, dye coupling was still evident among mutant interstitial cells, suggesting the presence of another connexin. This work raises the potential of the Cx43 deficient testes as a model for studies related to germ cell deficiency with normal Leydig cell functions in humans. Funded by the Canadian Institutes of Health Research.

KEY WORDS: Connexin43, Leydig cells, Androgens, Cell communication