Thermoacclimatory response of nucleic acid and protein content of carp muscle tissue: influence of growth rate and relationship to glycine uptake by scales

Abstract

RNA concentration in carp (Cyprinus carpio) white muscle tissue increased with higher growth rate for all acclimation temperatures, while DNA, protein content, and tissue hydration were unaffected. For a given growth rate, RNA concentration per unit tissue weight and per unit DNA (RNA per cell) was higher in colder acclimated fish as a probable compensation for decreased RNA activity. Maximum growth resulted in an approximate doubling of the RNA/DNA ratio while, over the range of 12–30 °C, cold acclimation caused an increase of approximately 50%. Changes in DNA concentration and protein/DNA ratios at different acclimation temperatures indicated an increase in cell mass with warmer acclimation temperatures. Muscle RNA/DNA ratios and the rate of glycine uptake by scales were highly correlated. Regression equations describing this relationship for each acclimation temperature were not significantly different when scales were incubated at each fish's acclimation temperature, but were significantly different when glycine uptake was expressed for incubation at the temperature of maximum uptake. These results suggest a whole-body integration between thermoacclimatory changes in the RNA component of muscle protein synthesis and in the rate of amino acid transport by scales.