The Fate of Arginine and Proline Carbon in Squid Tissues

Abstract

The metabolism of proline and arginine was investigated in kidney, gill, and heart of the pelagic squid, Symplectoteuthis. The rates of CO2 release from 14C-proline exceeded the rates from 14C-arginine. The metabolic rate of arginine and proline was assessed by monitoring the incorporation of arginine-derived carbon into various intermediates. Arginine was metabolized, through ornithine, to proline as well as to glutamate and various subsequent derivatives (alanine, octopine, aspartate, and carboxylic acids). The same components became labeled using 14C-proline as the starting substrate, but only the gill was capable of converting proline to arginine via the urea cycle. In addition, 14C-proline oxidation rates were high enough to exceed those of 14C-glucose in at least three tissues, kidney, heart, and inner mantle muscle.