Effects of salmon gonadotrophin (SG-G100) on plasma lipids in the goldfish, Carassius auratus

Abstract

Female goldfish were held under conditions of 12.degree. C and a 12 h light:12 h dark photoperiod during 3 phases of the sexual cycle. A pretreatment blood sample was taken after 2 wk of acclimation. Comparison of pretreatment levels of plasma lipids from the 3 experiments revealed that the concentration of triglycerides (TG) increased and total cholesterol (TC) decreased with increasing ovarian size. Plasma lipid phosphorus (LP) levels were slightly higher in sexually mature fish than in sexually regressed fish. Two wk after the pretreatment blood sample, the fish were injected i.p. with salmon gonadotropin (SG-G100) or control solution for 3 days, after which a posttreatment blood sample was taken. In sexually maturing fish SG-G100 injection caused increased plasma TG levels (compared with pretreatment) in fish with small ovaries, changing to decreased levels in fish with larger ovaries. A similar effect was also seen in maturing fish with plasma TC; these effects were abolished by castration or by keeping fish at 21.degree. C. SG-G100 had little effect on plasma LP. Gonadotropin evidently causes a net mobilization of lipid in fish with small ovaries (presumably via sex steroids) and accelerated ovarian uptake of lipid in fish with larger ovaries.