LOCALIZATION OF SPECIFIC PHOSPHATASE ACTIVITIES IN CANINE CORONARY BLOOD VESSELS AND HEART MUSCLE

Abstract

The localization of nonspecific alkaline phosphatase (AIPase), acid phosphatase (ACPase), nucleoside phosphatases (ATP-, ADP- and AMP-splitting enzymes), thiamine pyrophosphatase (TPPase) and glucose 6-phosphatase (G-6-Pase) activities was studied in coronary blood vessels and myocardium of the canine left ventricle. Except for AIPase and 5'-AMPase, the subcellular distribution of enzyme activities was essentially the same in arterial and venous vessels of different sizes, although enzyme activity varied in degree. Plasma membranes and pinocytic vesicles of intimal, medial and adventitial cells were reactive toward ATP, ADP and TPP. 5'-AMPase activity was seen at the cell membrane of adventitial or perivascular mesenchymal cells only. AIPase was confined to the endothelium of resistance vessels. Lysosomes and some Golgi complex showed moderate ACPase activity. Some Golgi cisternae and vesicles stained strongly with TPP as substrate. The endoplasmic reticulum and the nuclear envelope were constantly positive for G-6-Pase in every cell constituting the vascular wall. In the myocardial cell, ATPase activity was confined to the lateral elements of diads and triads, the subsarcolemmal cisternae and the mitochondrial matrix. Activity toward TPP and ADP was only seen in the Golgi apparatus. The few lysosomes present in myocardial cells possessed ACPase activity. G-6-Pase activity was uniformly distributed in the sarcoplasmic reticulum, the nuclear membranes, the subsarcolemmal cisterns and lateral elements of diads and triads.