Effects of chronic progressive myocardial hypertrophy on indexes of cardiac autonomic innervation.
The development of cardiac hypertrophy is associated with marked changes in cardiac autonomic innervation. Significant and sustained reductions of myocardial catecholamine stores and activities of tyrosine hydroxylase and dopamine beta-hydroxylase have been reported in models of acutely induced ventricular hypertrophy. Conversely, activity of choline acetyltransferase, a marker of parasympathetic nervous function, shows transient increases during the development of acute right ventricular hypertrophy. The potential physiological importance of these changes prompted us to examine a clinically more relevant model of slowly progressive ventricular hypertrophy. Application of a loose band around the pulmonary artery of weanling guinea pigs resulted in a growth-related progressive right ventricular pressure overload. Right ventricular weight-to-body-weight ratio was increased significantly and progressively at 9 and 18 weeks in banded animals (0.92 +/- 0.05 and 1.31 +/- 0.11 mg/g, respectively, p less than 0.01) compared with sham-operated controls (0.55 +/- 0.02 and 0.59 +/- 0.01 mg/g, respectively) but showed no further gain at 27 weeks (1.41 +/- 0.10 mg/g). Activities of tyrosine hydroxylase and dopamine beta-hydroxylase remained unchanged in all experiment groups, while right ventricular contents of norepinephrine in banded animals at 18 and 27 weeks exhibited sustained and progressive increases (2.45 +/- 0.11 and 3.40 +/- 0.19 micrograms/right ventricle, respectively) over controls (1.80 +/- 0.13 and 2.40 +/- 0.22 micrograms/right ventricle, respectively, p less than 0.01). The activity of choline acetyltransferase was markedly elevated in banded animals at 18 weeks (32.6 +/- 2.7 nmol/hr/right ventricle) but returned to baseline by 27 weeks (22.8 +/- 1.4 nmol/hr/right ventricle).(ABSTRACT TRUNCATED AT 250 WORDS)
- Copyright © 1987 by American Heart Association