PLASMA DISPOSAL RATE AND HEPATIC ALANINE METABOLISM IN PREGNANT AND NONPREGNANT RABBITS

To better define the glucose-alanine relationship and hepatic alanine metabolism during pregnancy, glucose and alanine turnover rates (TR) and simultaneous hepatic alanine uptake were determined in nine term pregnant (P) and 12 nonpregnant (NP) rabbits who had undergone chronic catheterization of both the systemic and hepatic circulations. [U-C-14(3)] Alanine and [3-H-3(1)] glucose were used as tracers. Whole animal [U-C-14(3)] alanine TR was significantly greater in P than in NP animals (42.7 +/- 1.7 versus 31.9 +/- 1.8 mu mol . min(-1), respectively, p < 0.001). However, there was no difference when the alanine TR was compared on a weight-specific basis (11.3 +/- 0.6 versus 9.6 +/- 0.6 mu mol . min(-1). kg(-1)). The glucose TR was higher in P compared with NP rabbits on both an absolute (122.3 +/- 6.2 versus 79.8 +/- 5.8 mu mol . min(-1), p < 0.001) and a weight-specific basis (32.9 +/- 1.4 versus 24.0 +/- 1.9 mu mol . min(-1). kg(-1), p < 0.005). Although the fraction of plasma glucose derived from plasma alanine in the whole animal was similar in P and NP animals (16.7% +/- 1.4 versus 13.9 +/- 0.7%, respectively), the absolute amount of plasma glucose derived from plasma alanine was greater in P rabbits (20.8 +/- 1.8 versus 11.2 +/- 1.2 mu mol . min(-1), p < 0.0005). In addition, the percentage of plasma alanine being converted to plasma glucose was greater in P than in NP animals (48.1 +/- 2.6 versus 34.6 +/- 2.0%, p < 0.001). There was no difference between P and NP rabbits in the fate of the C-14-label taken up by the liver in the form of [C-14] alanine + [C-14] lactate, with 62.9 +/- 5.9% (P) versus 65.2 +/- 6.0% (NP) released as [C-14] glucose, and 23.1 +/- 2.9% (P) versus 23.0 +/- 1.9% (NP) released as (CO2)-C-14. This is the first whole animal, nonacute study comparing hepatic alanine metabolism in P versus NP animals. In the rabbit, neither whole body or hepatic alanine metabolism was significantly altered by pregnancy.