Bioscientifica Proceedings

Summary. In calves made cryptorchid at birth, serum LH concentrations were elevated (P < 0.01) over those of intact controls by 7 weeks of age; a difference which persisted until after puberty. When intact and cryptorchid bulls were given LH-RH, i.v., at approximately 18 months of age, cryptorchid bulls were more responsive. Serum LH concentrations (mean ± s.e.m.) after 250, 1000 and 4000 ng LH-RH were 0.2 ± 0.03, 1.2 ± 0.3 and 12.1 ± 2.0 ng/ml for intact bulls and 1.0 ± 0.6, 5.1 ± 0.8 and 19.6 ± 2.1 ng/ml for cryptorchid bulls.

Testes from cryptorchid bulls weighed less (P < 0.01) than testes from intact bulls (68 ± 6 and 655 ± 36 g) at 24 months of age. Ability to secrete testosterone in vitro was determined by incubating minced pieces of testes at 36°C for 3 h in Krebs—Ringer—bicarbonate buffer (pH 7.2) containing 1 mg glucose/ml and 100 mi.u. hCG/ml. Cryptorchid testes secreted slightly more testosterone than scrotal testes on a unit weight basis, but when expressed on a paired testis weight basis, testosterone secretion by cryptorchid testes was less (8 ± 2 and 60 ± 10 mg, P < 0.01). Autoradiographic localization techniques were used to show the existence of LH/hCG binding sites in cryptorchid testes. These studies suggest that cryptorchid bull testes have a reduced capacity to secrete testosterone and the near-normal serum testosterone concentrations are maintained in the presence of increased serum gonadotrophins.

© 1981 Journals of Reproduction & Fertility Ltd