Appraisal of polyethyleneimine used as a tracer for anionic sites in human cardiac tissues with a brief reference to anionic molecular organization in altered basement membranes

Electron microscopic cytochemical studies on human ventricular muscles obtained during open heart surgery were carried out in ten patients with tetralogy of Fallot. Polyethyleneimine was used as a tracer for demonstration of anionic sites in the membrane surfaces of myocardial cells and capillaries. In the myocardial cells PEI particles were consistently observed to be orderly arranged in the external lamina of normal basement membranes at regular spacings of 40 to 80 nm. Few PEI particles were irregularly dispersed in the surface coat of basement membranes and the interspaces of intercalated discs. PEI particles were also seen to be regularly distributed in normal capillary basement membranes, mainly restricted in outer lamina densa at intervals of 40 to 80 nm. It was of particular interest that PEI particles were often seen to be irregularly and loosely arranged in abnormally thickened basement membranes of myocardial cells and capillaries. In addition, focal loss of PEI deposition in altered basement membranes was a frequent finding. Based on electron microscopic cytochemical findings the following conclusions are made: (1) The anionic sites characterized by PEI which is considered to be superior to most polycationic colloids show a regular lattice-like arrangement in the basement membranes of human myocardial cells and capillaries; (2) Anionic groups which are not distributed uniformly on human myocardial cell surfaces show different distribution patterns in the external lamina and surface coat of basement membranes; and (3) Perturbations of regular anionic arrays are demonstrable in altered basement membranes of diseased human myocardium.