AJP - Regulatory, Integrative and Comparative Physiology, Vol 245, Issue 6 827-R830, Copyright © 1983 by American Physiological Society
Metabolic organization of liver during spawning migration of sockeye salmon
C. J. French, P. W. Hochachka and T. P. Mommsen
Although earlier studies have established broad outlines of biochemical
changes during salmon spawning migration, the metabolic organization of
specific organs has hitherto remained unknown. In this study, we assessed
the performance of isolated liver cells from anorexic female sockeye salmon
(Oncorhynchus nerka) at four sampling sites along their 1,150-km spawning
migration. Isolated hepatocytes maintain high rates of gluconeogenesis and
CO2 release from amino acids and lactate throughout the migration. Alanine,
derived from proteolysis of white muscle, constitutes the single most
important source for de novo synthesis of glucose. Just before spawning,
when glycogen reserves reach a maximum, gluconeogenesis from alanine is
specifically inhibited, whereas its conversion to CO2 and the utilization
of other substrates are relatively unchanged. Spawning, apparently
supported by carbohydrate catabolism, is accompanied by depletion of
glycogen reserves from muscle as well as liver and a stimulation of
gluconeogenesis from amino acids. At the onset of migration, palmitate
oxidation accounts for about half the CO2 released by liver cells; its
contribution decreases during the migration and is negligible after
spawning.
