Increased uracil nucleotide metabolism during the induction of cardiac hypertrophy by beta-stimulation in rats.

The dynamics of uracil nucleotides was followed in the rat heart during the induction of cardiac hypertrophy by beta-adrenoreceptor stimulation. Isoproterenol (ISO) 5 mg . kg-1 was administered subcutaneously daily for 8 consecutive days. A significant increase in ventricular dry weight (40%) was observed on the 5th day of beta-stimulation, thereafter no further increase occurred. A single dose of ISO increased uridine triphosphate (UTP) concentration and the whole uracil nucleotide pool (UN). The increase was maximal (80 and 100%) 12 hours after ISO administration. The 32phosphate incorporation into the alpha-phosphate group of UN was increased by about a factor of 2 for the same period of time. Slight decrease in pool sizes (UTP and UN) and labelling occurred from 12 to 24 h after beta-stimulation. Similar changes also occurred on the 8th day of ISO administration, however modifications in concentrations and labeling were attenuated. The results show that modifications in the synthesis of UN should also be taken into account when studying the early events leading to cardiac hypertrophy.