Determination of the Local Erosion Stress of the Canine Endothelium Using a Jet Impingement Method

Abstract

A method to determine local endothelial erosion stress is presented. Freshly excised segments of middle descending thoracic aortas of dogs were slit open longitudinally and stretched in a specially designed rack to various circumferential and longitudinal dimensions. Jets of physiological saline were impinged normally on the endothelium of these segments. Lesions caused by the jet were made visible by staining the tissue with Evans blue dye. The dye solution was absorbed by regions where the endothelial layer had been damaged or destroyed. Characteristically, the lesions were annular in shape. This indicates that the endothelium can withstand large normal stresses where the jet impinges, but is eroded by the shear stress resulting from the jet efflux. Erosion stress of the endothelium was determined by correlating the external radius of a lesion with the shear stress expected at that radial distance from the center of the jet. Results from 185 lesions created in 17 aortic segments indicate that: 1) the in-vitro endothelial erosion stress as measured by a 30-s duration of exposure to shear stress is 7761 ± 155 (SEM) dynes/cm2 at room temperature (23° C) and 2645 ± 155 (SEM) dynes/cm2 at body temperature (37°C); 2) the erosion stress decreases markedly with an increase in the duration of exposure to shear stress; 3) the results for long-duration exposure are consistent with those of the well-known in-vivo study of Fry on endothelial erosion stress. The importance of the method is its ability to measure local endothelial erosion stress which is of particular significance in the study of the discrete process of atherogenesis.