AJP - Gastrointestinal and Liver Physiology, Vol 248, Issue 5 501-G506, Copyright © 1985 by American Physiological Society
Carbamoyl-phosphate synthetase I activity and ureagenesis in regenerating liver of the normal rat
M. W. Goodman and L. Zieve
Urea excretion per gram of liver was increased 219% 2-5 h post-partial
hepatectomy (Hx) and 45% 24-27 h post-Hx. Mitochondrial carbamoyl-phosphate
synthetase was also increased 5 h post-Hx but was not increased at 27 h. An
NH4+ load did not increase urea excretion per gram liver or the enzyme
activity noticeably in the 2- to 5-h period but did increase them 24-27 h
post-Hx. These results suggest that the enzyme activity and urea formation
per unit weight of liver were nearly maximal early during regeneration.
Orotic acid excretion per gram of liver in rats that received NH4+ was
increased more than 30-fold 2-5 h post-Hx and was similar in this respect
to nonhepatectomized rats. Ornithine prevented the increase in both normal
and hepatectomized rats, suggesting that ornithine was rate limiting for
the ornithine carbamoyltransferase (OCT) reaction. The orotic acid
excretion response to NH4+ was much less 24-27 h post-Hx, indicating that
ornithine availability for the OCT reaction may be increased at this time.
