Do androgens increase Leydig cell sensitivity to luteinising hormone?

Abstract

TARGET tissue responsiveness to hormones is not a static phenomenon, but is often influenced by the endocrine situation. For example, the sensitivity of the Leydig cell in the rat to luteinising hormone (LH) stimulation is not constant but gradually increases during prepubertal development1. Moreover, during treatment of hypogonadism in the human male, human chorionic gonadotrophin (hCG) therapy is often increasingly efficacious in stimulating testosterone secretion after repeated injections—a probable manifestation of induced target cell sensitivity. It is possible that androgen receptors in the Leydig cell2,3 are involved in the regulation of these changes in sensitivity. They are specific for testosterone and dihydrotestosterone4,5 and are distinct from the oestrogen receptors in the same cell3,6. We have investigated a possible role for these androgen receptors using the testicular feminised male (Tfm) rat. This rat has a male genotype and abdominal or inguinal testes, but a typical female phenotype because of a genetically determined lack of androgen receptors and a generalised target organ insensitivity to androgen7. We report here that the Leydig cells of the Tfm rat testis have much smaller number of LH/hCG receptors than normal, and this is associated with a low sensitivity to hCG.