Metabolism of poly (A)-containing mRNA in myocardium under normal physiological conditions and compensatory cardiac hyperfunction.

Two fractions of mRNA poly A+ and poly A- mRNA have been found in rat heart muscle by the method of affinity chromatography. These fractions amount to 30 and 70% of the total RNA respectively. The relationship between poly A+ and poly A-mRNA in myocardium does not alter in heart hyperfunction and aging. The life-span of mRNA reduces to 2-3 hours in the beginning of the process of myocardium hyperfunction development; the lifespan of mRNA does not differ from the controls in prolonged heart hyperfunction (6 months). The rate of poly A+mRNA synthesis increases by 70% compared to controls in the early stage of heart hyperfunction; it falls below the control level in long-term hypertrophied myocardium. This decreases in the rate of mRNA transcription in compensatory heart hypertrophy can play an important role in wear of the organ and in premature development of aging changes in the heart.