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The effect of experimental diabetes on phenylalanine metabolism in isolated liver cells.

ABSTRACT: Chronic (10-day) diabetes was associated with increased metabolic flux through phenylalanine hydroxylase in isolated liver cells. This flux was stimulated by 0.1 microM-glucagon, but not by 10 microM-noradrenaline; 0.1 microM-insulin affected neither basal nor glucagon-stimulated flux. The increased rate of phenylalanine hydroxylation in diabetes was accompanied by parallel increases in enzyme activity (as measured with artificial cofactor) and immunoreactive-enzyme-protein content. In contrast with total protein synthesis, which decreased, phenylalanine hydroxylase synthesis persisted at the control rate in cells from diabetic animals. These findings are discussed in relation to the hormonal regulation of the hydroxylase and the known metabolic consequences of chronic diabetes.

SUBMITTER: Santana MA

PROVIDER: S-EPMC1144822 | biostudies-other | 1985 Apr

REPOSITORIES: biostudies-other

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Phenylalanine metabolism in isolated rat liver cells. Effects of glucagon and diabetes.

Project description:1. Methods are described for monitoring the metabolic flux through phenylalanine hydroxylase, the tyrosine catabolic pathway and phenylalanine: pyruvate transaminase in isolated liver cell incubations. 2. The relationship between hydroxylase flux and phenylalanine concentration is sigmoidal. 3. Glucagon increases hydroxylase activity at low, near-physiological, substrate concentrations only. The hormone does not affect the rate of formation of phenylpyruvate. 4. Experimental diabetes (for 10 days) increases phenylalanine catabolism, and this is further increased by glucagon. 5. These results are discussed in the light of the known mechanisms for control of phenylalanine hydroxylase activity in vitro.

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The role of tryptophan 2,3-dioxygenase in the hormonal control of tryptophan metabolism in isolated rat liver cells. Effects of glucocorticoids and experimental diabetes.

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The metabolism of L-phenylalanine and L-tyrosine by liver cells isolated from adrenalectomized rats and from streptozotocin-diabetic rats.

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The influence of starvation and tryptophan administration on the metabolism of phenylalanine, tyrosine and tryptophan in isolated rat liver cells.

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Effect of glucagon on phenylalanine metabolism and phenylalanine-degrading enzymes in the rat.

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