Biochemical Correlates of Cardiac Hypertrophy

Abstract

Cardiac hypertrophy occurred in mature rats after producing supravalvular aortic stenosis with a specially designed silver clip. For 2 weeks following this procedure, heart weight, body weight, and RNA content of the myocardium were serially determined. Heart weight and RNA content increased within 24 hours of aortic banding, reaching a maximal level in 2 days and remaining elevated during the 2 weeks of observation. Nuclei were isolated and purified from heart muscle homogenates, and changes in RNA polymerase activity following aortic banding were determined. The nearest neighbor frequency of the bases of the RNA synthesized by the polymerase from nuclear preparations was identical in both the banded animals and the sham-operated controls. Both groups could thus be compared on the basis of the enzyme assay. RNA polymerase activity in nuclei from the hearts of banded rats rose rapidly when compared with the activity in sham-operated rats; peak values were reached on the second day, the earliest detectable change being around 12 hours. The increase in RNA polymerase activity represents one of the earliest biochemical events that take place in the myocardium following aortic banding.

A Ras-Dependent Pathway Regulates RNA Polymerase II Phosphorylation in Cardiac Myocytes: Implications for Cardiac Hypertrophy

“…Whether induced by pressure overload (55) or by ␣ 1 -adrenergic (5), AII, or phorbol ester (3) stimulation, hypertrophy is also accompanied by an increase in total RNA content. This in turn may be a result of the associated increases in RNA polymerase activities (43) and the rate of RNA synthesis (25,31). Although an increase in total RNA might sufficiently explain the increase in total protein that we observed, it does not exclude a superimposed effect on translation or on ribosome biogenesis.…”

Metabolism of thyroid hormones in cultured cardiac fibroblasts of neonatal rats

“…Measured by cell numbers, however, the fibroblast is the most abundant cell type in the heart, constituting an estimated two-thirds of the total cardiac cell population (Nair et al 1968, Agocha & Eghbali-Webb 1997. The thyroid status of an animal not only affects cardiomyocyte function, but also that of cardiac fibroblasts.…”

β2‐ADRENOCEPTORS REGULATE INDUCTION OF MYOCARDIAL ORNITHINE DECARBOXYLASE IN MICE in vivo

“…Catecholamines have been repeatedly implicated in cardiac hypertrophy in studies of exogenously administered isoprenaline, adrenaline or noradrenaline (Fisher, Horst & Kopin, 1965;Nair, Cutilletta & Rabinowitz, 1968;Stanton, Brenner & Mayfield, 1969;Feldman & Russell, 1972;Laks, Morady & Swan, 1973;Byus, Chubb, Huxtable & Russell, 1976). Three fold elevations of the endogenous plasma catecholamine, adrenaline, have been shown to parallel cardiac hypertrophy in the dog (Womble, Haddox & Russell, 1978) whereas ablation of plasma adrenaline by adrenal medulla denervation prevents cardiac hypertrophy after aortic constriction (Womble, Larson, Copeland, Brown, Haddox & Russell, 1980).…”