Hormonal regulation of gluconeogenesis and glycogenolysis in carp ( Cyprinus carpio) liver pieces cultured in vitro

Abstract

1. 1. Pieces of carp liver ( Cyprinus carpio) were cultured in vitro for up to 14 days. 2. 2. Gluconeogenesis from lactate was maintained for at least 14 days in culture and there was no relationship between the rate of gluconeogenesis and either the length of time in culture or the glycogen content of the liver. 3. 3. Adrenaline, glucagon and Cortisol each significantly increased the gluconeogenic rate from lactate after 1, 7 and 14 days of culture. 4. 4. Adrenaline and glucagon also consistently increased the rate of hepatic glycogenolysis, whereas the effects of cortisol were both less consistent and smaller. 5. 5. The rate of glycogenolysis was at least 5, and generally more than 20 times the rate of gluconeogenesis. 6. 6. These findings support existing evidence that adrenaline, glucagon and cortisol are all involved in the regulation of hepatic gluconeogenesis in teleosts. 7. 7. Adrenaline and glucagon also regulate hepatic glycogenolysis, as has been reported for other teleosts and mammals. 8. 8. When hepatic glycogen is available, glycogenolysis is probably more important than gluconeogenesis in supplying glucose to the blood from the liver.