AJP - Endocrinology and Metabolism, Vol 244, Issue 6 548-E554, Copyright © 1983 by American Physiological Society
Liver ornithine decarboxylase in pregnant rats fed two levels of casein
Y. Hitier, O. Champigny and G. Bourdel
Liver ornithine decarboxylase (ODC) and tyrosine aminotransferase (TAT)
activities were assessed at 2200 h (prandial phase) and at 1000 h
(postprandial phase) in virgin and in pregnant (day 13-20) rats fed on
different levels of casein and carbohydrate. In virgin rats, ODC levels
were higher at 2200 h after resumption of eating than at 1000 hours, the
inductive effect being greater with the high-casein than with the
low-casein diet. Rapid deinduction followed termination of eating,
resulting in equally low enzyme levels at 1000 h with both diets. On the
contrary, prandial and postprandial levels of TAT were always greater with
the high-protein diet. In pregnant rats, there was a progressive
stimulation of ODC that reached a maximum on day 19. However, the inductive
capacity of the high-protein diet was lower than that of the low-casein
diet. Prandial rest was not followed by enzyme deinduction at 1000 h. In
contrast, TAT stimulation remained dependent on overall casein ingestion.
At constant casein but restricted carbohydrate intake, pregnant females
exhibited a reduction in ODC stimulation. Thus, whereas in virgin females
proteins are determinant in the regulation of ODC, during pregnancy there
determinant in the regulation of ODC, during pregnancy there is a shift
toward modulation by carbohydrates. Levels of liver urea and ornithine were
found to vary in inverse proportion with the magnitude of ODC stimulation.
