A number of studies report that isolated Krebs-perfused hearts deteriorate with time, develop edema, and demonstrate a progressive increase in coronary vascular resistance. However, hearts perfused with filtered blood are more stable with regard to cardiac function and coronary resistance. The changes observed in the Krebs hearts may be due to a "permeability"-type edema. The purpose of this study was to systematically determine whether adding protein and blood cells to a Krebs perfusate affected coronary microvascular permeability to macromolecules. The rat heart preparation employed allowed direct visualization and quantification of transcoronary macromolecular leakage. We observed severe transcoronary leakage of fluorescent albumin (FITC-BSA) when FITC-BSA was later added after 20 min of perfusion with Krebs. Leakage was decreased by including 2 g/100 ml albumin (BSA) in the initial perfusate but was not further reduced by increasing the BSA concentration to 5 g/100 ml. However, adding washed blood cells to the initial perfusate did further reduce FITC-BSA leakage. The index of FITC-BSA exchange, the O/I ratio, was 0.70 +/- 0.02 (+/- SE) for Krebs perfusate, 0.55 +/- 0.03 for Krebs-BSA, and 0.45 +/- 0.02 for Krebs-BSA-blood cells, indicating significant effects for both protein and blood cells (P less than 0.05). The results suggest that both protein and blood cells are necessary to maintain the semipermeable characteristics of the coronary exchange vessels.
Myocardial microvascular permeability, interstitial oedema, and compromised cardiac function
