EFFECT OF CERTAIN HIGH CARDIAC-OUTPUT STATES ON DOG HEART MYOSIN ATPASE

This work was done to evaluate the response of cardiac myosin ATPase in the compensated heart subjected to the increased volume work of a high cardiac-output state. Dogs with bilateral femoral arteriovenous fistulas were studied either 14 days (acute arteriovenous fistulas) or a mean of 230 days (chronic arteriovenous fistulas) after construction of the fistulas. Dogs with anemia secondary to repeated bleeding (anemic) were studied 14 days after a high output state was first documented. Calcium-activated myosin adenosine-triphosphatase (ATPase) activity was significantly elevated for the anemic and acute arteriovenous fistula dogs, but the elevations were not significant for myosin from the chronic arteriovenous fistula dogs. In the presence of K+ and EDTA, the cardiac myosin ATPase activity was generally elevated for the anemic, less so for the acute arteriovenous fistula and was normal for the chronic arteriovenous fistula. The Ca2+ uptake (in the presence of oxalate) by the cardiac sarcoplasmic reticulum was significantly less than normal for all three groups. © 1979.