[Effect of 17 alpha hydroxy-20 beta dihydroprogesterone and progesterone on maturation and ovulation in vivo and on the plasma level of gonadotropic hormone t-GtH in rainbow trout Salmo gairdneri].

Ovulation occurred 5 to 9 days after injection of 2 mg/kg 17 alpha-hydroxy-20 beta dihydroprogesterone (17 alpha-20 beta Pg) in rainbow trout with oocytes in which the germinal vesicle was subperipheral. Whereas oocyte maturation was initiated by 17 alpha-20 beta Pg without an immediate increase in the concentration of t-GtH, in controls an increased level was found to coincide with initiation of the process and the concentration of t-GtH was higher at all stages. Progesterone treatment was less effective.