Glutamine Oxidation by Developing Rat Small Intestine

Abstract

Glutamine has been reported to be a major oxidative substrate in adult rat small intestine. The significance of glutamine by developing rat jejunal tissue slices and isolated mitochondria was determined. Jejunum slices from suckling rats actively oxidized glutamine at rates significantly greater than adult slices. Increasing the glutamine concentration (0.5-4 mM) in the assay increased glutamine by jejunum of suckling pups by 30% compared to a 100% increase in adult jejunum. Glutamine oxidation by isolated jejunal mitochondria was similar in suckling and adult rat. Glutamine oxidation by jejunum of suckling rat was increased in the presence of 5 mM glucose whereas adult glutamine oxidation was not affected by exogenous glucose. Glutamine inhibited glucose oxidation by jejunum of both suckling and adult rats. In adult jejunal homogenates alanine aminotransferase activity was 2-fold greater than in suckling animals. In the presence of 10 mM aminooxyacetate, a known inhibitor of alanine aminotransferase, glutamine oxidation by jejunum of suckling rat was inhibited by 95%, suggesting that alanine aminotransferase is a major metabolic pathway for the oxidation of glutamine.