Long-Term Effects of Ribose on Adenine Nucleotide Metabolism in Isoproterenol-Stimulated Hearts
It is well established that isoproterenol stimulates cardiac ß-adrenergic receptors1 and induces a positive inotropic effect which is Ca++-mediated and which eventually leads to a decline of the ATP concentration2,3, isoproterenol also induces an enhancement of the biosynthesis of myocardial adenine nucleotides (AN) in rat hearts3, which, however, is not of such a magnitude that it has an appreciable effect on the diminution of the ATP concentration. This seems to be mainly due to the fact that cardiac AN biosynthesis is limited by the available pool of 5-phosphoribosyl-1-pyrophosphate (PRPP) which is supplied by the hexose monophosphate shunt4,5. Ribose which bypasses the hexose monophosphate shunt has been shown to overcome this limitation thus leading to an elevation of the available PRPP pool and to an increase of the biosynthesis of AN in rat hearts in vivo4. On the basis of these findings studies were performed to examine whether ribose may affect the isoproterenol-induced diminution of cardiac ATP concentration when applied as continuous i.v. infusion over a longer period of time.
KeywordsAdenine Nucleotide Positive Inotropic Effect Ehrlich Ascites Tumor Cell Hexose Monophosphate Purine Ring
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