Abstract
Experiments were performed to determine if catecholamines can regulate control points in the gluconeogenic pathway, such as mitochondrial pyruvate carboxylation and pyruvate kinase activity, via an alpha-adrenergic, adenosine 3':5'-monophosphate-independent mechanism. Of a number of alpha agonists tested, only norepinephrine, epinephrine, and phenylephrine caused an increase in mitochondrial pyruvate metabolism. The effects of catecholamines on pyruvate carboxylation were not attenuated by 1-propranolol which abolishes changes in cyclic nucleotide levels but were blocked by alpha antagonists such as ergotamine, phenoxybenzamine, and phentolamine. Time course experiments demonstrated that the effects of catecholamines on the mitochondria and on carbohydrate metabolism correlated temporally with the concentration of epinephrine in the medium but not with the small changes in adenosine 3':5'-monophosphate. The effects of catecholamines appeared to require extracellular Ca2+ ion. The observation that catecholamines do not increase gluconeogenesis to the same extent as glucagon was not due to a differential effect on mitochondrial CO2 fixation. Rather, catecholamines caused a smaller inhibition of pyruvate kinase activity than did glucagon. The effects of catecholamines on pyruvate kinase also appeared to be mediated by an alpha-adrenergic, adenosine 3':5'-monophosphate-independent mechanism.
Highlights
IntroductionOf a number of u agonists tested, only norepinephrine, epinephrine, and phenylephrine caused an increase in mitochondrial pyruvate metabolism
Experiments were performed to determine if catecholamines can regulate control points in the gluconeogenie pathway, such as mitochondrial pyruvate carboxylation and pyruvate kinase activity, via an LY
The effects of catecholamines on pyruvate kinase appeared to be mediated by an n-adrenergic, adenosine 3’:5’-monophosphate-independent mechanism
Summary
Of a number of u agonists tested, only norepinephrine, epinephrine, and phenylephrine caused an increase in mitochondrial pyruvate metabolism. The effects of catecholamines on pyruvate carboxylation were not attenuated by 1-propranolol which abolishes changes in cyclic nucleotide levels but were blocked by cyantagonists such as ergotamine, phenoxybenzamine, and phentolamine. Time course experiments demonstrated that the effects of catecholamines on the mitochondria and on carbohydrate metabolism correlated temporally with the concentration of epinephrine in the medium but not with the small changes in adenosine. The observation that catecholamines do not increase gluconeogenesis to the same extent as glucagon was not due to a differential effect on mitochondrial. Catecholamines caused a smaller inhibition of pyruvate kinase activity than did glucagon. The effects of catecholamines on pyruvate kinase appeared to be mediated by an n-adrenergic, adenosine 3’:5’-monophosphate-independent mechanism
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