The influence of ischemia and reperfusion on nucleotide concentration in human myocardium was investigated during heart and heart-lung transplantation. Myocardial preservation during heart transplantation was achieved by infusion of cold St. Thomas' Hospital cardioplegic solution followed by storage in Ringer's solution at 4 degrees C during transport. In contrast, the hearts of heart and lung donors were preserved by core cooling using cardiopulmonary bypass and infusion of cold blood cardioplegia containing 26 mM potassium. The heart-lung block was transported in cold donor blood. Nucleotides and their catabolite concentrations were measured in donor tissue specimens taken before organ collection, before commencement of implantation and 30 min after aortic clamp removal. During reperfusion, samples of coronary sinus and arterial blood were collected and analysed for nucleotide catabolite concentration. Myocardial ATP and total nucleotide pool remained almost unchanged during the ischemic transport of the donor organs with only very small increases in myocardial inosine and hypoxanthine concentrations. However, a significant decrease of total adenine nucleotide pool by 10%-20% was demonstrated between the start of implantation and 30 min post-reperfusion. A release of inosine + hypoxanthine was greatest in the 1st minute (15-25 microM), but was still substantial after 10 min of reperfusion (5-15 microM). Metabolic changes tended to be more pronounced during heart-lung transplantation than during heart transplantation.