Hepatic glucose production in rainbow trout: Effects of sustained exercise and epinephrine.

Abstract

The role of carbohydrate metabolism is not yet established in fish. Therefore, the goal of my thesis was to quantify the rate of hepatic glucose production (Ra glucose) during aerobic exercise in fish. During sustainable exercise, mammals strongly stimulate their rate of hepatic glucose production to replace the additional glucose consumed by locomotory muscles and this increase in Ra glucose may be regulated by circulating catecholamines. By analogy with mammals, I hypothesized that sub-maximal exercise in trout will increase hepatic glucose production above resting levels. Circulating catecholamines were also measured to establish their possible influence in stimulating Ra glucose. To test this hypothesis, I measured the rate of appearance of glucose in rainbow trout swimming for 3 h at 1.5 body lengths s-1. Results indicated that circulating EPI could be a possible candidate for regulating Ra glucose during exercise. Therefore, I investigated the effects of sympathetic EPI on Ra glucose (1) by infusing exogenous EPI to increase plasma concentrations and (2) by blocking the effect of sympathetic EPI via beta-adrenoreceptors with propranolol (PROP). I hypothesized that EPI will stimulate whereas PROP will depress hepatic glucose production. (Abstract shortened by UMI.)