Intratesticular steroids and gonadotrophin receptor concentrations in the testes of immature unilaterally cryptorchid rats.

Testicular descent was prevented unilaterally in newborn rats. In this experimental model of cryptorchidism the first morphological changes are noted in the abdominal testis at 16 days of age. Testicular weight was increased in the abdominal testis at 16 days of age, was unaffected at 20 days but was decreased at 30 days of age. The concentrations of LH and FSH receptors, and the hCG-stimulated progesterone and testosterone secretion in vivo were analysed in scrotal and abdominal testes at different ages. LH- and FSH-receptor content per testis were unaffected by cryptorchidism at 12, 16 and 20 days of age but were depressed markedly at 30 days of age. At 20 days of age (but not earlier) hCG-stimulated progesterone was reduced while testosterone secretion remained unchanged. It is concluded that the early functional changes in abdominal testes are not related to changes in gonadotrophin receptor content.