The effect of germ cell complement on the presence of oxytocin in the interstitial and seminiferous tubule fluid of the rat testis

Abstract

Abstract 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 interstitial fluid (IF) and seminiferous tubule fluid (TF) of the rat and whether concentrations of the peptide vary within the two compartments following germ cell destruction. In order to destroy germ cells adult male rats were anaesthetized and their scrotal regions placed in a water bath at 43 °C for 20 min. Control animals were subjected to anaesthesia alone. Groups of 6 animals were killed 3, 7 and 21 days after heat treatment and their testes removed for histological examination or fluid extraction. IF and TF were separated and the oxytocin content of the fluids measured by radioimmunoassay. Immunoreactive oxytocin 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 authentic peptide following HPLC. Three days after heat treatment IF levels of oxytocin were significantly reduced but TF levels of the peptide were significantly increased. These changes were associated with a lack 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 pachytene spermatocytes were removed using the testicular toxicant methoxyacetic acid. To investigate whether oxytocin passes from the IF into the TF, 3H-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 3H-oxytocin passed from the IF into the TF. These data suggest that the seminiferous tubule as well as the Leydig cells may secrete oxytocin and that this secretion may be influenced by the presence of germ cells, particularly pachytene spermatocytes. Journal of Endocrinology (1994) 143, 471–478