Hormonal and Dietary Control of Enzymes in the Rat: II. Effect of Pancreatectomy and Adrenalectomy on Some Liver Enzymes Unique to Amino Acid Metabolism and Gluconeogenesis

Abstract

In the liver of pancreatectomized rats the activities of ornithine δ-transaminase [EC 2.6.1.13] and histidine ammonia-lyase [EC 4.3.1.3] were lowered significantly. The low activity of ornithine δ-transaminase in pancreatectomized rats was not elevated in response to an amino acid supply which caused 3 fold increase in the enzyme activity in sham-operated rats. The level of tyrosine transaminase [EC 2.6.1.5] in pancreatectomized rats which survived for 3 days or more after the operation was not significantly different from normal, although the enzyme activity was elevated several fold for 48 hr after pancreatectomy. In parallel with the lower activities of amino acid metabolizing enzymes, less liver protein was lost on 4 days starvation following pancreatectomy than in sham-operated rats. The elevation of phosphoenolpyruvate carboxykinase [EC 4.1.1.32] activity on starvation was not significantly affected by either pancreatectomy or adre-nalectomy, but largely reduced by the absence of both the adrenals and pancreas. Possible mechanisms by which the activities of some liver enzymes are lowered or elevated after pancreatectomy are discussed.