Hypothesis: control of hepatic utilization of alanine by membrane transport or by cellular metabolism? Review.

The rate of alanine transport into the liver limits its utilization even under the high alanine load resulting from a 90% casein diet, given that the rat has been adapted to that diet. A coordinated acceleration of alanine catabolism allows transport to remain rate-limiting, which in turn allows the adaptive regulation of transport to remain effective at high alanine loads. Accelerated degradation of alanine may change the hepatic amino acid content in a way that derepresses the activity of the alanine carrier system(s).