1.- Depariamento de Ciencias Ecológicas. Facultad de Ciencias, Universidad de Chile. Casilla 653, Santiago, Chile.
2.- Unidad de Biología de la Reproducción. INTA, Universidad de Chile, Santiago, Chile.
Ovulatory response and GtH II serum levels in female rainbow trout (Oncorhynchus mykiss) with GnRHa D-Ala6 induced ovulation
The ovulatory response and GtH serum levels were studied in female rainbow trouts induced with GnRHa DAla6 (Syndel). Induced females (group 1, n = 50) were injected with 30 mg/kg of body weight
of GnRHa applied in two doses of 15 mg/kg of body weight each, with and interval of 6 days. Control females (group 2, n = 21) were simultaneously injected with a saline placebo. The ovulatory
rcsponse of induced females. measured as an accumulated percentage of ovulated females post-treatment, was significantly higher than the control group (p < 0.01). GtH II serum levels were
determined by radioimmunoassay (RIA) in samples collected 6 h after each hormone injection. Of the 18 induced females, 15 showed detectable values: 14.7 ± 3.6 ng/ml (n-6) after the first
injection, and 16.6 ± 3.1 ng/ml (n=9) after the second injection. Only 3 fish showed a value of serum GtH II below the range detected by the assay (> 1.94 ng/ml). GtH II serum levels of the
control group were undetected after the first injection (n=10) and only one female showed a value of 2.52 ng/ml after the second injection of the hormona. Both, the ovulatory response and the
serum GtH II values confirm the capacity of GnRHa D-Ala6 to stimulate ovulation through and increase in GtH II synthesis and/or secretion from the pituitary gland. Hormonal induction with
parenteral injection appears to be an appropriate tool for the synchronization of spawning in cultured rainbow trout.
Palabras claves: inducción de ovulación, gonadotrof'ina, trucha.
Keywords: induction of ovulation, gonadotropin, rainbow trout.