Genetic differences in androgen receptors and in autoregulation of testicular human chorionic gonadotropin binding sites in the mouse.

The autoregulation of testicular human chorionic gonadotropin (hCG) binding sites was studied in two strains of mice known to differ in their endocrine and reproductive characteristics (C57BL/10J and DBA/2J), and in their F1 progeny (B10D2F1). Basal hCG binding levels were higher in C57BL/10J than in DBA/2J mice, while B10D2F1 mice had intermediate levels. Twenty-four h after injection, hCG produced dose-related changes in hCG binding in C57BL/10J and B10D2F1 mice not observed in DBA/2J mice. However, 72 h after treatment with hCG there was a decrease in hCG binding in all the strains studied. These results suggest the participation of genetic factors in determining basal levels, dose-related changes and temporal response of testicular hCG binding sites to hCG administration. Androgen receptor levels were measured in the same strains of mice. DBA/2J mice had higher receptor levels in the kidney and coagulating gland, and lower levels in the hypothalamus and seminal vesicle when compared to C57BL/10J mice. B10D2F1 mice had androgen receptor levels similar to those measured in C57BL/10J mice in all tissues studied, with the exception of the coagulating gland, where levels were similar to those observed in DBA/2J mice. These observations may indicate the existence of several loci coding for androgen receptors, with only one being expressed per tissue.