EVIDENCE FOR A PROTEIN-LIKE FACTOR FROM RETE TESTIS FLUID THAT SUPPRESSES LUTEINIZING-HORMONE-RELEASING HORMONE (LHRH) PULSES (LHRH STATIN)- A NEW HORMONAL ACTIVITY

Signals that modulate LH-releasing hormone (LHRH) pulse frequency are fundamental mechanisms for regulating important reproductive processes . Gonadal steroids are presently considered to account for the entire gonadal feedback mechanism that modulates LHRH secretion. However, we have previously suggested that a testicular protein(s) present in char coal-treated rete testis fluid (ctRTF) can suppress LH pulsatility in the ram. The present experiments were aimed at determining whether the disappearance of LH pulses induced by ctRTF administration implicate a hypothalamic or a pituitary site of action. Thus, we have examined t he effects of ctRTF peripheral administration on 1) the LH response to LHRH, 2) LHRH portal blood levels, and 3) LHRH content in hypothalami c tissue. Finally, the effects of ctRTF administered into the third ve ntricle on plasma LH levels were assessed. The present results show th at a testicular protein(s) is able to suppress LHRH pulse frequency wi thout affecting amplitude and without any effect on the LH response to LHRH (LHRH Statin). The observation that an active dose administered by the intracerebroventricular route is 0.0005 the active dose needed by the peripheral route reinforces this evidence. These data lead to t he new concept that the testicular signals that govern LHRH pulse freq uency may be not only steroids, but also proteins.