Polypeptide composition and histopathologic changes in endomyocardial biopsies from transplanted human hearts.

Sequential postoperative samples of 43 human right ventricular endomyocardial biopsies from four heart transplant patients were evaluated histopathologically to assess microscopic parameters of rejection. Selected pieces of these myocardial biopsies were weighed and homogenized in low ionic strength buffer containing Triton X-100 to extract and to quantitate cardiac actin. Aliquots of the soluble fractions were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Residual pellets were solubilized and also underwent SDS-PAGE. Electrophoretograms were analyzed densitometrically. Actin from biopsies from transplanted human hearts accounted for approximately 40% of Triton X-100 soluble polypeptides. Actin and myosin heavy chain content in the pellet fractions was unchanged as a function of allograft duration. A polypeptide band resolved between 14,000 and 21,000 daltons in the Triton-soluble fraction of four fresh samples correlated with histopathologic changes of moderate acute allograft rejection. A similar band was noted in 11 frozen endomyocardial biopsy specimens without changes of acute rejection. Small actin differences may be found in the transplanted heart, but they do not correlate with rejection. The presence on SDS-PAGE of the polypeptide band found between 14,000 and 21,000 daltons may correlate with proteolysis of cytoplasmic proteins either from rejection or possibly from autolysis after freezing.