Intratesticular factors and testosterone secretion: the role of luteinizing hormone in relation to changes during puberty and experimental cryptorchidism.

Testicular interstitial fluid (IF) from the rat contains a nongonadotropic polypeptide factor (or factors) which can enhance human CG (hCG)-stimulated testosterone production by Percoll-purified Leydig cells in vitro. The potential importance of this factor has been investigated by measuring its effective levels in testicular IF from individual rats during sexual maturation or after the induction of unilateral cryptorchidism (UCD). In both situations, the effect of modulating LH drive to the testis was also assessed. In abdominal testes from UCD rats, levels of the IF factor were nearly doubled (P less than 0.001) when compared to levels in the contralateral scrotal testis; this was associated with more than an 85% reduction in IF testosterone levels. Further lowering of testosterone levels by the injection of an antiserum to LH beta, raised levels of the IF factor by 30-40% (P less than 0.01) in both scrotal and abdominal testes. Conversely, raising of testosterone levels by injection of hCG caused more than a 90% reduction (P less than 0.001) in levels of the IF factor in both scrotal and abdominal testes. During sexual maturation, levels of the IF factor doubled (P less than 0.01) between 30 and 40 days of age, remained high until 70 days of age, and then decreased to the lower levels found in adult rats. High pubertal levels of the IF factor were associated with the most rapid phase of testicular growth and with a steady increase in the IF levels of testosterone. Injection of pubertal or adult rats with antiserum to ovine LH (oLH) reduced testosterone levels by approximately 85% and doubled (P less than 0.01) levels of the IF factor(s) in both groups. It is concluded that levels of the IF-factor are influenced: by testosterone levels and/or LH drive and by the maturational and/or functional status of the testis. These results also suggest that changing levels of the IF factor may be of physiological significance during puberty.