A novel approach for assessing protein synthesis in channel catfish, Ictalurus punctatus

A comprehensive understanding of animal growth requires adequate knowledge of protein synthesis (PS), which in fish, has traditionally been determined by the flooding dose method. However, this procedure is limited to short-term assessments and may not accurately describe fish growth over extended periods of time. Since deuterium oxide (2H2O) has been used to non-invasively quantify PS in mammals over short- and long-term periods, we aimed at determining if 2H2O could also be used to measure PS in channel catfish. Fish were stocked in a 40-L aquarium with ~ 4% 2H2O and sampled at 4, 8 and 24 h (n = 6 at each time period) to determine 2H-labeling of body water (plasma), as well as protein-free and protein-bound 2H-labeled alanine. The labeling of body water reflected that of aquarium water and the labeling of protein-free alanine remained constant over 24 h and was ~ 3.8 times greater than that of body water. By measuring 2H-labeled alanine incorporation after 24 h of 2H2O exposure we were able to calculate a rate of PS: 0.04 ± 0.01% h− 1. These results demonstrate that PS in fish can be effectively measured using 2H2O and, because this method yields integrative measures of PS, is relatively inexpensive and accounts for perturbations such as feeding, it is a novel and practical assessment option.