Restitution of myocardial adenine nucleotides: acceleration by administration of ribose.

In the present study, the influence of ribose on the biosynthesis of myocardial adenine nucleotides was examined in rats in vivo utilizing two experimental models which are characterized by a reduction in the adenine nucleotide content; recovery from oxygen deficiency and application of isoproterenol. 1. The biosynthesis (= de novo synthesis) of cardiac adenine nucleotides was enhanced by 90% during the first 60 min of recovery from five intermittent periods of asphyxia of 4.5 min duration (Table I). 2. Isoproterenol induced a stimulation of myocardial adenine nucleotide synthesis in a dose-dependent manner amounting to 640% three hours after s.c. administration of 25 mg/kg (Fig. 1). 3. Ribose which bypasses the hexose monophosphate shunt in the myocardium and which leads to an elevation of the available pool of 5-phosphoribosyl-1-pyrophosphate (PRPP), stimulated the biosynthesis of adenine nucleotides in the heart, but not in liver and kidney, of rats one hour after i.v. application of a single dose of 100 mg/kg from 6 nmoles/g/h to 27 nmoles/g/h (Fig. 2). 4. When ribose was constantly infused during the first 60 min of recovery from asphyxia, the enhancement of cardiac adenine nucleotide biosynthesis was further stimulated from 12.6 nmoles/g/h to 20.5 nmoles/g/h (with 500 mg ribose/kg/h) and to 43.4 nmoles/g/h (with 1 000 mg ribose/kg/h) (Fig. 3). 5. Continuous I.V. infusion of ribose (200 mg/kg/h) for 24 hours in isoproterenol-treated rats during a 13-fold increase in myocardial adenine nucleotide biosynthesis compared with the control (Fig. 4). In this condition, the isoproterenol-induced decline in the adenine nucleotide level did not occur (Table II).