Chemiluminescence measurements of xanthine oxidase and xanthine dehydrogenase activity in four types of cardiovascular cell.

The activity and location of xanthine oxidase (EC.1.2.3.2.) and xanthine dehydrogenase (EC.1.2.1.37) have been measured using luminol-enhanced chemiluminescence in four types of cell from the cardiovascular system (neonatal and adult rat cardiac myocytes, rat aortic vascular smooth muscle cells, rat cardiac fibroblasts and human umbilical vein endothelial cells). The detection system developed was both rapid and reproducible and could be used on sub-milligram quantities of cells. Xanthine oxidase was located primarily in cells derived from the vasculature and especially in endothelial cells, as was xanthine dehydrogenase. Only neonatal myocytes had more dehydrogenase activity than oxidase. The significance of the location and activity of these enzymes is discussed in relation to the pathology of myocardial ischaemia, arrhythmogenesis and microvascular disorders.