Cortisol-induced changes in some aspects of the intermediary metabolism of Salvelinus fontinalis.

Cortisol was administered to brook charr (Salvelinus fontinalis) in the form of slow-release intraperitoneal implants (a) to investigate the effect of chronic cortisol stimulation (up to 60 days) on various aspects of intermediary metabolism, and (b) to determine whether such cortisol-induced changes were comparable to those seen in chronically fasted charr. Except for fish sampled at 1 and 6 h after implantation, there was no consistent increase in the plasma cortisol levels of the cortisol-implanted animals. Nevertheless, there were significant treatment effects (particularly after 60 days) on certain metabolite levels, and key hepatic enzymes, including a lowering of plasma glucose and hepatic glycogen concentrations, increased activities of FBPase, G6PDH, GK, and G3PDH, and reduced activities of PFK. When taken together these changes are indicative of a direct or indirect gluconeogenic action of cortisol, in which metabolites other than amino acids (possibly glycerol) are utilized as substrates. These metabolic changes differed from those found in food-deprived brook charr which appeared to use proteins, as well as lipids, as energy sources.