PITUITARY-TESTICULAR AXIS IN RATS LACKING TESTICULAR MACROPHAGES

Testicular macrophages were depleted selectively in adult rats by intr atesticular injections of liposome-entrapped dichloromethylene diphosp honate (Cl2MDP-lp), whereas control animals received intratesticular i njections of phosphate-buffered saline-containing liposomes or 0.9% Na Cl. The absence of macrophages in Cl2MDP-lp-injected rats was confirme d histologically. Rats lacking testicular macrophages showed significa ntly increased (twofold on average) serum concentrations of luteinizin g hormone at 5 and 10 days after treatment. Serum luteinizing hormone concentrations drop to control values at 15 days after treatment. Seru m testosterone concentrations were increased significantly (twofold on average) at 5, 10 and 15 days after treatment. No significant changes were found for follicle-stimulating hormone serum concentrations, or for the weights of the testes and sex accessory organs. Testicular his tology was unchanged, except for the absence of testicular macrophages in Cl2MDP-lp-treated animals. Rats treated with NaCl or Cl2MDP-lp wer e injected with 100 IU of human chorionic gonadotrophin and sacrificed 2 h later. Serum testosterone concentrations increased 8.6- and 3.5-f old in NaCl and Cl2MDP-lp-treated rats, respectively, in response to a cute human chorionic gonadotrophin treatment. These results point out the relevance of testicular macrophages for the regulation of the pitu itary-testicular axis.