Myofibrillar ATPase activity in the carp Cyprinus carpio: interactions between starvation and environmental temperature.

The myofibrillar ATPase activity of the epaxial white muscle was measured in carp Cyprinus carpio L. acclimated to 10 degrees C or 28 degrees C. As previously reported, cold acclimation was associated with an increase in the ATPase specific activity and a decrease in the thermostability. The water content of the white muscle was significantly higher in cold-acclimated fish than in warm-acclimated fish (P less than 0.002). Starvation for 10 weeks resulted in a significant increase in the white muscle water content of both warm- and cold-acclimated fish (P less than 0.002). When carp were starved, the ability of the myofibrillar ATPase to show thermal compensation disappeared. Previously acclimated fish, when starved, showed steady alterations of the myofibrillar ATPase activity to a level mid-way between the acclimated extremes. Refeeding resulted in a gradual return to the normal acclimated level.

Protein synthesis in tissues of fed and starved carp, acclimated to different temperatures.

The temperature dependence of the rates of protein synthesis in the red and white skeletal muscle of the carp (Cyprinus carpio) was measured using a method which involved a single injection of tritiated phenylalanine. Plasma and muscle-free phenylalanine quickly reached a plateau level at all temperatures. During the plateau phase the incorporation of label into protein was liner. Muscle from fish previously acclimated to either a low temperature (8°C) or a high temperature (28°C), showed marked differences in the rates of protein synthesis. The results show that cold acclimation is associated with significantly higher rates of protein synthesis (p<0.001) in both red and white muscle. Arrhenius activation energies, derived from the rates of protein synthesis at the different experimental temperatures, were similar for both red and white muscle in fish acclimated to warm or cold temperatures. Measurements for both acclimated groups over the temperature range 8-34°C showed that the activation energy for the process of protein synthesis was 86.7 kJ/mol and 78.7 kJ/mol for the red and white muscle respectively.