Cardiac myosin phenotype remodelling following adrenodemedullectomy and chronic 6-hydroxydopamine in male Sprague-Dawley rats.

Background: An increase was previously found in relative beta myosin heavy chain (MyHC) in the right ventricle of rats following thoracic spinal transection. It was hypothesized that the MyHC remodelling that was observed might be due, in part, to autonomic influences on the right ventricle.

Objective: To evaluate cardiac myosin phenotype following 21 days of reduced sympathetic activity.

Methods: Adult male Sprague-Dawley rats underwent either adrenodemedullectomy/chemical sympathectomy (SX) or sham operation/sham injection (CN). Twenty-one days following surgery, the animals were sacrificed and both ventricles were harvested. The ventricles were denatured and run on sodium dodecyl sulfate-polyacrylamide gel electrophoresis for identification of MyHC isoforms.

Results: SX resulted in a significant decline in catecholamines. In the right ventricle, beta MyHC ratio was twofold higher in SX animals than in CN rats, but there was no difference between groups in beta MyHC concentration in the left ventricle (P<0.05). Uniquely, we found a decrease in relative alpha MyHC in the right ventricle but no change in the myosin phenotype in the left ventricle.

Conclusions: These data potentially indicate that MyHC concentrations in the left ventricle are less sensitive than the right ventricle to decreased sympathetic activity.