Effects of cortisol on hepatic carbohydrate metabolism and responsiveness to hormones in the sea raven,Hemitripterus americanus |
| |
Authors: | M M Vijayan G D Foster T W Moon |
| |
Institution: | (1) Huntsman Marine Science Centre, St. Andrews, New Brunswick, Canada, EOG 2X0;(2) Ottawa-Carleton Institute of Biology, Department of Biology, University of Ottawa, Ottawa, Ontario, KIN 6N5, Canada;(3) Department of Animal Science, Faculty of Agricultural Sciences, 248 2357 Main Mall, Vancouver, B.C., V6T 1Z4, Canada |
| |
Abstract: | The sea raven, Hemitripterus americanus, is a sit-and-wait, low metabolic rate, marine teleost. The objective of this study was to determine i) whether cortisol implantation (50 mg. kg-1) for 7 days altered hepatocyte metabolism, and hepatocyte responsiveness to epinephrine, glucagon and insulin, and ii) whether 8 weeks of food-deprivation modified the above response. Cortisol implantation significantly increased hepatocyte
total glucose production and oxidation from alanine compared to the sham group. There was no cortisol effect on glycogen breakdown,
suggesting that the activation of other pathways, including gluconeogenesis, are required to account for the increased glucose
production. Epinephrine-mediated (10-5M) glycogen breakdown and insulin-mediated (10-8M) total glucose production were enhanced in hepatocytes of cortisol implanted sea ravens, but there were no change in any
glucagon (10-7M) effects. The enhanced glycogen breakdown in the absence of similar increases in total glucose production with epinephrine
indicates mobilization of carbohydrate reserves for endogenous use by the liver.
Food-deprivation for 8 weeks significantly decreased condition factor, plasma cortisol concentration and liver glycogen content
in the sea raven, but had no effect on plasma glucose concentration. Hepatocyte total glucose production and flux rates from
alanine increased significantly with food-deprivation. Moreover, food-deprivation increased responsiveness of total hepatocyte
glucose production to the actions of glucagon and insulin, but not to epinephrine; none of these effects were modified by
cortisol implantation.
Our results indicate that cortisol in the sea raven exerts both a direct and an indirect or permissive effect on hepatocyte
metabolism by modifying hepatocyte responsiveness to epinephrine and insulin stimulation. Cortisol implantation did not modify
the effects of glucagon or food-deprivation in this species. |
| |
Keywords: | cortisol sea raven teleosts Hemitripterus americanus gluconeogenesis glycogenolysis metabolism hepatocytes insulin epinephrine glucagon |
本文献已被 SpringerLink 等数据库收录! |
|