Abstract
Since glutamine is the preferred oxidative substrate in suckling rat jejunum, we determined in developing rat jejunum the activity of alanine aminotransferase, one of three enzymes that converts glutamate to 2-oxoglutarate. The jejunal activity of alanine aminotransferase in cytosolic supernatant is 0.24±0.02 (umol of pyruvate/mg prot/hr) in suckling pups and 0.39±0.04 in postwean pups. Amino-oxyacetate is a known inhibitor of alanine aminotransferase. We determined the effect of amino-oxyacetate on glutamine, glucose and 3-hydroxybutyrate(3-HB) oxidation by adult rat jejunum. Glutamine oxidation to CO2 and glucose oxidation to lactate, an indicator of glycolysis, is inhibited by 80%. Glucose oxidation to CO2 is inhibited 40%. 3-HB oxidation is activated by 340%. These data suggest that the major pathway by which glutamine oxidation enters the citric acid cycle is through alanine aminotransferase. Glycolysis is inhibited by amino-oxyacetate. In the absence of glutamine oxidation and glycolysis 3-HB oxidation is activated indicating a high potential for intestinal oxidation of ketones. values = means ± S.E.(no.=4) All oxidation rates in which amino-oxyacetate is added are different than control (p<0.01). We conclude that if glucose and glutamine oxidation is suppressed, ketone oxidation can be a major source of energy in rat jejunum.
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