Effect of Endurance Swimming on the Lactate Kinetics of Rainbow Trout

Abstract

The lactate turnover rate of rainbow trout (Oncorhynchus mykiss) was measured by bolus injection of [U-14C]lactate at rest and during prolonged swimming at 85% Ucrit to determine the importance of this metabolic fuel for endurance locomotion in fish, to assess whether lactate exchange between white and red muscle could be a possible mechanism for supplying oxidizable fuel to their lateral red muscle, and to compare the contribution of lactate to total energy provision between teleost and mammalian species. Turnover rate only increased from 4.41 +/− 0.33 to 9.71 +/− 1.69 mumol kg-1 min-1 between rest and prolonged swimming, and the contribution of lactate oxidation to total metabolism declined during exercise. Lactate exchange between white and red muscle is, therefore, not a significant mechanism to fuel the active lateral red musculature during prolonged swimming. The lactate turnover rate of teleosts is one or two orders of magnitude lower than in mammals of equivalent size, but lactate has the same importance as a fuel in both vertebrate groups. However, lactate turnover rate and oxidation rate do not scale with body mass in the same fashion as does metabolic rate. The slope of the mammalian relationship for whole-body lactate turnover and oxidation is much lower (0.58) than the slope of the classic relationship for metabolic rate (0.75), indicating that lactate is a much more important oxidative substrate for small than for large animals.

EcoPhysioMechanics: Integrating Energetics and Biomechanics to Understand Fish Locomotion under Climate Change

“…Kinematics of swimming influence the costs of locomotion, but physiological processes can, in turn, affect movement. Several studies have shown that the ratio of lactate produced:disposed increases at intermediate-to-high speeds ( Weber 1991 ; Peake and Farrell 2004 ; Svendsen et al 2010 ). The increase of lactate in body fluids and tissues limits the swimming performance of fishes ( Black et al 1962 ; Jain et al 1998 ; Kieffer 2000 ; Jain and Farrell 2003 ; Widmer et al 2006 ).…”