Rates of polypeptide chain assembly in liver in vivo: relation to the mechanism of temperature acclimation in Opsanus tau.

A simple translational model, present herein, permits experimental determination of the rates of protein synthesis in vivo in terms of a time constant representing the average assembly time of the polypeptide chains. The model has been used to interpret incorporation of radioactive amino acids into toadfish liver fractions as a function of time after hepatic portal vein injection. The results suggest that the increase in liver protein synthesis produced by cold acclimation is due to a more rapid rate of addition of amino acid residues to the growing polypeptide chains. The finding is consistent with the greater aminoacyl transferase activity in livers of cold-acclimated fish.