Konventionelle und molekularpathologische Untersuchungen während und nach klinischer Herztransplantation

Different preservation of myocardial capillary endothelial cells and cardiomyocytes during and after cardioplegic ischemia (25 degrees C) of canine hearts

Complete resumption of cardiac function after cardioplegic arrest presupposes a well-preserved myocardial ultrastructure during and after ischemia. Therefore, we determined ischemia-induced ultrastructural alterations in the myocardium during and after reversible cardioplegic ischemia using stereological methods. Cardiac arrest was induced with St. Thomas' Hospital- or Custodiol (HTK) solution. Reperfusion with Tyrode's solution followed after reversible cardioplegic ischemia in situ. Samples were taken 1) from beating hearts, 2) from cardioplegically arrested hearts immediately after the end of coronary perfusion, 3) from ischemic hearts incubated in the cardioplegic solution at 25 degrees C, and 4) from reperfused beating hearts after ischemia in situ at 22 degrees C. Cellular swelling was determined as the barrier thickness of capillary endothelium and as the sum of cardiomyocyte volume fractions of free sarcoplasm and mitochondria. In St. Thomas'-arrested hearts, intraischemic volume increase was significantly more pronounced in endothelial cells than in cardiomyocytes. Reperfusion at the intraischemic practical limit of resuscitability (ATP levels of 4 micromol/gww) significantly reduced intraischemic swelling of cardiomyocytes, but not of capillary endothelial cells. Mitochondrial damage was more pronounced in capillary endothelial cells during ischemia and after reperfusion. Thus, after reversible cardioplegic arrest, structural recovery of cardiomyocytes is better than that of capillary endothelial cells. An incomplete structural protection of capillary endothelial cells may predominantly contribute to postischemic dysfunction in the reperfused heart.

Right ventricular upregulation of the Ca(2+) binding protein S100A1 in chronic pulmonary hypertension

The Ca(2+) binding protein S100A1 increases the Ca(2+) release from the sarcoplasmatic reticulum by interacting with the ryanodine receptor. In order to understand whether this effect might be operative in the early course of hypertrophy, when myocardium is able to meet increased workload, we investigated the expression of S100A1 in a model of moderate right ventricular hypertrophy. The pulmonary arteries of nine pigs were embolised three times with Sephadex G-50. After 70 days, all pigs showed a moderate pulmonary hypertension. Right ventricular tissue of embolised animals showed a significant increase of connective tissue and enlargement of myocyte diameters. In controls, we found a differential expression of S100A1 with significantly lower S100A1 protein levels in right ventricular compared to left ventricular tissue. In pulmonary hypertension, S100A1 expression increased significantly in hypertrophied right ventricles while it was unchanged in left ventricular tissue. No change was observed in the expression of SERCA2a and phospholamban. Our data show, for the first time, that moderate pressure overload results in an upregulation of S100A1. This may reflect an adaptive response of myocardial Ca(2+) homeostasis to a higher workload.