INDUCIBLE HEAT-SHOCK-PROTEIN-70 IN RAT CARDIAC ALLOGRAFT AND ITS IMMUNOHISTOCHEMICAL LOCALIZATION IN CARDIAC MYOCYTES

Background, Heat shock proteins (HSP) are induced by a variety of stre ss and are presumed to play an important role in protecting cells from the effects of stress, Some evidence exists that HSP is involved in a llograft rejection, Recently, an increase of inducible HSP 70 in heter otopic rat heart allografts was shown by quantitative Western blotting , To determine a possible mRNA induction and the localization of induc ible HSP 70, we examined 19 heart transplants in rats, Methods, Fisher F344 rat hearts were heterotopically transplanted into Lewis recipien ts (n = 10), and nine cardiac isografts (Fisher to Fisher) were perfor med, The 19 native hearts of the recipients served as controls, Animal s were killed on posttransplantation days 1, 3, and 5, The hearts were examined immunohistologically for inducible HSP and analyzed by a sem iquantitative polymerase chain reaction for inducible mRNA, Results, T he level of HSP 70 mRNA in the allograft increased from day 1 to 3 and day 3 to 5 after transplantation and was significantly higher than th at of time-matched isografts (0.92 +/- 0.49 vs, 0.49 +/- 0.05 and 1.14 +/- 0.53 vs. 0.53 +/- 0.15; P < 0.05), The native hearts showed no el evated HSP 70 expression compared with isografts. Immunohistochemicall y, the majority of inducible HSP was located in cardiomyocytes adjacen t to infiltrating lymphocytes, which where consistently negative. Conc lusions, These results demonstrate that HSP mRNA expression in cardiac allografts is time-dependent, and its protein is expressed in cardiom yocytes.