Lipid mobilization in rainbow trout (Oncorhynchus mykiss).

Abstract

Even though lipids are thought to be a major metabolic fuel in fish during aerobic activity, little is known about their mobilization. Therefore, the goal of my thesis was to quantify lipid mobilization in fish. By analogy with mammals, I hypothesized that when fish are subjected to submaximal exercise, they mobilize their triacylglycerol (TAG) reserves above resting levels, which would result in: (1) increases in fatty acid (NEFA) and glycerol appearance rates (also termed fluxes), and (2) a decrease in the percent of NEFA reesterified by the TAG:FA substrate cycle. To test this hypothesis, I measured NEFA and glycerol rates of appearance, and I calculated the intracellular TAG:FA cycling rate in rainbow trout swimming for 1 h at either 1.0 or 1.5 bl s$\sp{-1},$ and 4 days at 1.0 bl s$\sp{-1}.$ This study is the first to measure glycerol appearance rate and TAG:FA cycling in fish. This thesis demonstrates that during submaximal exercise fish do not mobilize their triacylglycerol reserves above their resting levels. This result contrasts with what was expected by analogy to the mammalian situation or from body composition studies in exercising fish. (Abstract shortened by UMI.)