[Evolution of plasma levels of glycoproteic gonadotropins and of 17 alpha hydroxy-20 beta dihydroprogesterone during maturation and ovulation of rainbow trout, Salmo gairdnerii].

The plasma concentrations of the glycoproteic gonadotropin (GTH) and of the 17 alpha hydroxy-20 beta dihydroprogesterone (17 alpha 20 beta OHP) have been followed in the course of ovulation in 6 rainbow trout, using radioimmunoassays on samples taken every two days. A first slow and limited GTH increase (10 to 20 ng/ml) is detected before and during the ovulation, while the 17 alpha 20 beta OHP rises sharply (up to three to five hundreds nanogrammes per millilitre). Then the progestagen levels drop back to their previous values, for about three weeks after ovulation. At the same time, a second higher GTH increase (25 to 20 ng/ml) is taking place. The relations between these two hormones, maturation and ovulation are discussed.