Capillary permeability in canine myocardium as determined by bolus injection, residue detection

Abstract

Capillary permeability of 51Cr-EDTA in the canine myocardium was determined by applying the single injection, external registration method and the local tissue clearance method, to the intact dog heart of open-chest anesthetized dogs, 51Cr-EDTA was administered into the left anterior descending coronary artery as a bolus injection and the response curve was recorded by external registration. The capillary diffusion capacity (the permeability-surface area product) for 51Cr-EDTA amounted to 32.5 ml/100 g .cntdot. min at a capillary extraction of 0.40 and a plasma flow of 73.3 ml/100 g .cntdot. min. The diffusional permeability coefficient of 51Cr-EDTA was calculated to 1.08 .times. 10-5 cm/s which indicates that the permeability of the capillaries in the myocardium for 51Cr-EDTA is similar to that of continuous capillaries in other tissues. 51Cr-EDTA (3-100 .mu.l) was injected at a depth of 5 mm into the myocardium of the left ventricular free wall and the residue curve was recorded. The capillary extraction, as determined by the tissue clearance method, was calculated to values 6 times smaller than determined with the single injection, residue detection method. This unreasonably low extraction was probably due to methodological errors inherent to the tissue clearance technique.