Protein Metabolism and Cold Adaptation in Antarctic Fishes

Abstract

Protein synthetic rates have been determined in vivo at −1.5 C by the method of constant infusion in four species of Antarctic fish of McMurdo Sound of genus Trematomus (Nototheniidae) and Gymnodraco (Bathydraconidae). Parameters for liver protein synthesis were obtained by pulse injection and infusion methods in T. hansoni. Protein synthetic rates in liver averaged 6% of tissue protein per day. Synthetic rates in the other tissues studied fell in the following order: foregut > liver > gill = spleen = head kidney > trunk kidney > red muscle > white muscle. Rates in liver and white muscle are compared with data for temperate and tropical fishes at habitat temperatures and at reduced temperatures. The theoretical temperature dependency for protein synthetic reactions based on studies in temperate species is taken as Q10 = 2.5. The results indicate a twofold adaptation for liver protein synthesis and a threefold adaptation for white muscle in the Antarctic species relative to predicted values. Rates in white muscle of freshly caught T. hansoni and T. bernacchii averaged 0.22% of tissue protein per day, declining to 0.05% per day with 5–15 days starvation. The data suggest that as much as three-fourths of protein synthesis in white muscle of these species is directed toward growth under normal summer feeding conditions. The results are compared with growth data for T. bernacchii.