Contrasting effects of spontaneous and induced cardiomyopathy on the nucleoproteins of turkey hearts.

The possible involvement of nuclear proteins in the pathogenesis of cardiomyopathy was studied in a spontaneously occurring and a furazolidone-induced model of turkey cardiomyopathy. Both models are characterised by cardiac hypertrophy and dilatation, systemic hypotension and depressed contractility. The protein composition of myocardial nuclei was compared in normal (n = 9) and cardiomyopathic (spontaneous n = 6, furazolidone-induced n = 21) turkeys. Cardiac nuclei from spontaneously myopathic animals had a higher histone content (1.827 +/- 0.058 (mean +/- SD) mg . mg DNA-1 vs 1.688 +/- 0.187 in controls, P less than 0.05) and histone/nonhistone protein ratio (1.122 +/- 0.020 vs 0.882 +/- 0.128 in controls, P less than 0.01). Nuclear protein phosphorylation was lower in spontaneously cardiomyopathic turkeys primarily because of decreased nonhistone protein phosphorylation (5.100 +/- 0.759 pmol 32 P . mg prot-1 .15 min-1 vs 8.456 +/- 0.886 in controls, P less than 0.01). In contrast, furazolidone-induced cardiomyopathy of similar severity to the spontaneously occurring model was not associated with changes in nucleoprotein composition or degree of phosphorylation. These results indicate that development of spontaneous cardiomyopathy in turkeys may be related to the composition and function of nuclear nonhistone proteins. These changes are not secondary to the cardiac hypertrophy/dilatation accompanying the myopathic process.