Testosterone treatment augments LHRH-a induced ovulation in greenback flounder

Greenback flounder were treated with either an injection of des Gly(10) [D- Ala(6)] 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 significant ly increase the number of ovulatory events above control levels. Treatment with LHRH-a+T stimulated more ovulatory events than treatment with LHRH-a a lone, suggesting T increases pituitary responsiveness to LHRH-a. Plasma lev els of 17 beta -estradiol (E-2) were significantly higher in fish treated w ith LHRH-a and LHRH-a+T than in control fish or fish treated with T. Plasma levels of 17,20 beta -dihydroxy-4-pregnen-3-one were not elevated above co ntrol levels. Daily ovulations, elevated E-2 and T levels and presumably el evated GtH-II levels, persisted well after the expected clearance time of e xogenous LHRH-a. Positive steroid feedback may have contributed to the proc esses of repeated final oocyte maturation and ovulation.