DEMONSTRATION OF ADENYL CYCLASE ACTIVITY IN CANINE CARDIAC SARCOPLASMIC RETICULUM

A microsomal fraction from canine cardiac muscle that actively accumulates calcium has been found to exhibit adenyl cyclase activity. The enzyme responds in a characteristic manner to fluoride and norepinephrine. Electron microscopic studies of the microsomal fraction demonstrate that it contains intact membrane vesicles; the lack of any glutamic dehydrogenase activity suggests that no contaminating mitochondrial fragments are present. In view of its active calcium accumulating ability, this fraction is believed to represent fragments of sarcoplasmic reticulum. This report represents the first demonstration of adenyl cyclase in cardiac sarcoplasmic reticulum. © 1969.