QUANTITATIVE MORPHOLOGICAL CORRELATIONS OF ALTERATIONS IN CAPILLARY-PERMEABILITY, FOLLOWING HISTAMINE AND MODERATE BURNING, IN MOUSE DIAPHRAGM - AND EFFECTS OF BENZOPYRONES

The effects of moderate burning and histamine on capillaries were studied in the diaphragms of mice by EM, quantitative stereology. Many junctions were opened, but these closed again after .apprx. 30 min. Ten junctions which were open over parts of their depths were studied by serial sectioning. These represented junctions which were actually completely open, from the lumenal to the ablumenal surfaces, but in planes other than those of the sections. The calculated permeabilities of the capillaries while they had many open junctions were much greater than those found by experiment. The connective tissue, not the endothelium, is the factor limiting small molecular passage; the injured vessels are, temporarily, tunnel-capillaries. The small vesicles were slightly altered, although the reduction in the cellular widths may have increased transport via this system by .apprx. 50%. They did not increase their diameters. Great numbers of large vacuoles appeared and were just as frequent 90 min after the injuries. If, as appears likely, these transport material across the cells, they would correspond with the physiological deductions. The effects of a mixture of 2 benzopyrones were studied. These increased the numbers of open junctions, but had negligible effects on the vesicles and vacuoles. While it is known that these drugs greatly reduce high-protein edemas, including those of burns, this indicates that they do not do this by reducing capillary permeability.