The Utilization of 14 C-Labeled Lactate,Pyruvate and Alanine by Prelactating Tissues and Hyperplastic Alveolar Nodule Outgrowths 1

Abstract

Summary

The utilization of ¹⁴C-labeled lactate, pyruvate and alanine by specimens of prelactating tissue taken from pregnant mice and hyperplastic alveolar nodule outgrowths from C3H mice was investigated. In the absence of glucose, CO₂ production and fatty acid synthesis from these substrates was higher in the prelactating mammary gland than in the hyperplastic alveolar nodule outgrowths. Addition of glucose effected a decrease in CO₂ production from all 3 carbons, but caused an increase in fatty acid formation from the second and third carbons of these substrates. This effect by glucose was proportionately similar in both tissues. Lactate uptake by the prelactating mammary gland was about 60% higher than that by the hyperplastic alveolar nodule outgrowths, but amino acid formation from this substrate was markedly higher in the latter tissue. The activity of the citrate condensing enzyme (EC 4.1.3.7) was considerably lower in the hyperplastic alveolar nodule outgrowths than in the prelactating mammary tissue. An enzymatic alteration at this site would slow entry of 3-carbon glycolytic intermediates into the Krebs cycle and may represent a prime metabolic lesion in the development of the hyperplastic alveolar nodule outgrowths.