Mechanism of 3-phenylpyruvate-induced insulin release. Metabolic aspects. |
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| Authors: | W J Malaisse A Sener M Welsh F Malaisse-Lagae C Hellerstrm and J Christophe |
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| Affiliation: | W J Malaisse, A Sener, M Welsh, F Malaisse-Lagae, C Hellerström, and J Christophe |
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| Abstract: | 1. The metabolism and metabolic effects of 3-phenylpyruvate were examined in rat pancreatic islets. 2. Islet homogenates catalysed transamination reactions between 3-phenylpyruvate and L-glutamate, L-leucine, L-norleucine or L-valine. 3-Phenylpyruvate failed to activate glutamate dehydrogenase. 3. 3-Phenylpyruvate rapidly entered into islet cells, was extensively converted into phenylalanine but slowly oxidized. 4. The conversion of phenylpyruvate into phenylalanine coincided with a fall in the content of several amino acids (especially glutamate and aspartate) in the islets and incubation medium, the accumulation of 2-oxoglutarate and a modest fall in the NH4+ production rate. 5. 3-Phenylpyruvate failed to affect 14CO2 output from islets prelabelled with U-14C]palmitate, but augmented 14CO2 output from islets prelabelled or incubated with L-U-14C]glutamine. 6. In the presence of L-glutamine, 3-phenylpyruvate augmented the ATP/ADP ratio and NAD(P)H islet content, and caused a rapid and sustained decrease in the outflow of radioactivity from islets prelabelled with 2-3H]adenosine. 7. These data support the view that the insulin-releasing capacity of 3-phenylpyruvate coincides with an increase in the catabolism of endogenous amino acids acting as 'partners' in transamination reactions leading to the conversion of 3-phenylpyruvate into phenylalanine. |
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