The effects of cold storage and type of preservation solution on coronary endothelial function are not well understood. Experiments were designed to evaluate coronary endothelial-dependent relaxation after a 4-hr cold (4 degrees C) storage in different preservation solutions. Isolated rat hearts were studied in the Langendorff apparatus for coronary endothelial function. After 30 min of stabilization, hearts were arrested with a 10-min perfusion of 4 degrees C crystalloid hyperkalemic cardioplegic solution (CHCS) containing 24 mmol/L of KCl and stored for 4 hr in the following preservation solutions: CHCS, Krebs-Ringer's solution (KR), 0.9% NaCl (NS), and University of Wisconsin solution (UW). A fifth group was perfused and stored in UW solution. Endothelial-dependent and independent coronary artery vasorelaxation were tested, respectively, by infusing 5-hydroxytryptamine (5-HT) (1 x 10(-6) mol/L) and sodium nitroprusside (SNP) (1 x 10(-5) mol/L) before and 30 min after the storage period. In hearts stored in CHCS and KR, the coronary artery flow increase to 5-HT and SNP infusion were not significantly affected. However, in hearts preserved with NS and UW solutions, 5-HT coronary response was significantly decreased, indicating endothelial dysfunction. In addition to these findings, coronary flow increase to SNP infusion was decreased in the group perfused and stored with UW, suggesting smooth muscle damage. These experiments suggest that 4-hr cold storage in NS or UW impairs endothelial-dependent coronary relaxation in the isolated rat heart model.