THE EFFECT OF GERM-CELL COMPLEMENT ON THE PRESENCE OF OXYTOCIN IN THEINTERSTITIAL AND SEMINIFEROUS TUBULE FLUID OF THE RAT TESTIS

In the rat testis oxytocin has been localized to the Leydig cells, and these cells have been shown to produce oxytocin in vitro. The present study was performed to determine whether oxytocin is present in the i nterstitial fluid (IF) and seminiferous tubule fluid (TF) of the rat a nd whether concentrations of the peptide vary within the two compartme nts following germ cell destruction. In order to destroy germ cells ad ult male rats were anaesthetized and their scrotal regions placed in a water bath at 43 degrees C for 20 min. Control animals were subjected to anaesthesia alone. Groups of 6 animals were killed 3, 7 and 21 day s after heat treatment and their testes removed for histological exami nation or fluid extraction. IF and TF were separated and the oxytocin content of the fluids measured by radioimmunoassay. Immunoreactive oxy tocin was detected in both the IF (100 +/- 11 pg/ml) and TF (27 +/- 4 pg/ml) of control rats and this immunoreactivity co-eluted with the au thentic peptide following HPLC. Three days after heat treatment IF lev els of oxytocin were significantly reduced but TF levels of the peptid e were significantly increased. These changes were associated with a l ack of pachytene spermatocytes in the histological sections. Seven and 21 days after heat treatment the levels of oxytocin in the IF and TF were not significantly different from control levels. Similar changes in IF and TF oxytocin levels were seen in a second experiment when pac hytene spermatocytes were removed using the testicular toxicant methox yacetic acid. To investigate whether oxytocin passes from the IF into the TF, H-3-oxytocin was infused into the testicular arteries of both control and heat-treated rats and the rats killed at regular intervals over the next 24 h. In both groups of animals <5% of the H-3-oxytocin passed from the IF into the TF. These data suggest that the seminifer ous tubule as well as the Leydig cells may secrete oxytocin and that t his secretion may be influenced by the presence of germ cells, particu larly pachytene spermatocytes.