ABSTRACT
Phosphorylase activity has been investigated histochemically under controlled conditions in the specialized tissue and the general myocardium of goat heart using glucose-1-phosphate as the substrate. It has been observed that the phosphorylase content of the nodal and conducting tissue is very high as compared to the general myocardium. The phosphorylase content of the cardiac neural elements is also high. Since the connective tissue which surrounds the nodal and conducting tissue has almost no phosphorylase activity, the nodal and conducting tissue is sharply demarcated by the histochemical reaction for phosphorylase. This reaction can, therefore, be used as a specific and expedient method for the localization of specialized tissue as an exploratory and confirmatory test.
Subject(s)
Myocardium/enzymology , Phosphorylases/isolation & purification , Animals , Atrioventricular Node/enzymology , Bundle of His/enzymology , Goats , Histocytochemistry , Purkinje Fibers/enzymology , Sinoatrial Node/enzymologyABSTRACT
It was observed that the heart rate was minimum at zero transmural pressure. The mean heart rate at zero transmural pressure was 23+/-5/min. This mean heart rate increased from 23+/-5/min to a peak value of 40+/-6/min (74% acceleration) when the transmural pressure was raised from 0 to +4 mm Hg and to a similar peak value of 36+/-8/min (56% acceleration) when the transmural pressure was lowered from 0 to -4 mm Hg. The peak values attained at +/-4 mm Hg were highly significant (p less than 0.001). It is concluded that the heart rate at zero transmural pressure represents the basic intrinsic pacemaker frequency independent of neural, humoral, thermal and haemodynamically induced mechanical influences.
