Alanine turnover rate and its hepatic metabolism are increased in midpregnant rat

At mid pregnancy (12th day) fed rats exhibit a drop of blood alanine level when the weight of the fetoplacental unit is still negligible. A primed infusion A-V method was used to measure alanine kinetics in fed midpregnant rats and virgin controls, using L-[2,3-3H]alanine as a tracer. Alanine turnover and metabolic clearance rates were higher on day 12 than in virgin controls. The increase in alanine turnover rate was accounted for by an increase in alanine degradation. Since the liver is the main site of alanine degradation, alanine uptake was studied in isolated hepatocytes. Hepatocytes isolated from midpregnant rats utilized 50% more alanine than those from virgin controls. This increase was mainly due to metabolism rather than incorporation into proteins. In conclusion, the alanine turnover rate and its hepatic metabolism are increased in fed midpregnant rats, resulting in the decrease in blood alanine.