Profiles of Sex Steroids in Wild-caught Carp Cyprinus carpio carpio Linnaeus 1758 During Ovulation Induction by Acute Versus Sustained Delivery Methods of Different GnRHa Analogues

The effects of acute versus sustained delivery methods of GnRHa on sex steroid profiles of wild-caught female carp Cyprinus carpio carpio Linnaeus 1758 (Cyprinidae) were studied in fish receiving 20 μg.kg^−1 mammalian or salmon GnRHa in acute (Linpe method) or sustained delivery methods, i.e., cholesterol pellets (Chol) and emulsion of GnRHa (GnRHa-FIA).Negative and positive control fish were injected by physiological saline (control) and 4 mg.kg^−1 carp pituitary extract (CP), respectively. Plasma steroid levels of testosterone (T), 17β-estradiol (E2) and 17α, 20β-dihydroxy, 4-pregnone, 3-one (DHP) were measured by RIA at 0, 6, 12, 24 and 48 h after final injection. Plasma level of T decreased after final injection in almost all treatment groups and gradually increased thereafter, and peaked at ovulation time (from 0.56±0.12 in sChol to 1.50±0.56 ng.mL^-1 in CP). E2 levels showed similar changes in almost all treatments with an increase at ovulation time (from 0.46±0.14 in sChol to 1.69±0.93 ng.mL^-1 in CP) and a decrease afterwards except for Chol groups in which the levels of E2 decreased at ovulation time. Plasma DHP levels showed a surge at the ovulation time (from 14.27±3.27 in mlinpe to 21.80±17.44 ng.mL^-1 in sLinpe) before a rapid decrease in all groups except for Chol groups in which the levels of DHP gradually increased during ovulation induction and remained high even after 48 h (from 7.92±1.4 in mChol to 9.37±0.76 ng.mL^-1 in sChol).