Testosterone treatment augments LHRH‐a induced ovulation vin greenback flounder

Abstract

Greenback flounder were treated with either an injection of des Gly10 [D‐Ala6] LHRH ethylamide (LHRH‐a), a silastic pellet implant of testosterone (T) or LHRH‐a+T. LHRH‐a and LHRH‐a+T induced more ovulatory events than in control fish or fish treated with T alone. T treatment did not significantly increase the number of ovulatory events above control levels. Treatment with LHRH‐a+T stimulated more ovulatory events than treatment with LHRH‐a alone, suggesting T increases pituitary responsiveness to LHRH‐a. Plasma levels of 17β‐estradiol (E 2) were significantly higher in fish treated with LHRH‐a and LHRH‐a+T than in control fish or fish treated with T. Plasma levels of 17,20β‐dihydroxy‐4‐pregnen‐3‐one were not elevated above control levels. Daily ovulations, elevated E 2 and T levels and presumably elevated GtH‐II levels, persisted well after the expected clearance time of exogenous LHRH‐a. Positive steroid feedback may have contributed to the processes of repeated final oocyte maturation and ovulation.