EFFECTS OF HEAT-SHOCK AND A CARCINOGEN (1,2-DIMETHYLHYDRAZINE) ON THETIME-DEPENDENT P53 PROTEIN-CONCENTRATION IN THE RAT SERUM

Background - We have studied the expression of the cytoplasmic (solubl e) form of p53 protein in animals exposed both to heat shock and to a Carcinogen. Methods - Rats were treated with hyperthermia (2h at 45 de grees C) or with a carcinogen (1,2-dinethyhydrazine, DMH, 20 mg/kg wee kly for 5 weeks). The results were evaluated by-the determination of t he serum levels of proteins that were isolated by the method described (25). Results - Hyperthermia:caused an increase in concentrations of 90; 70 and 53-kD proteins 2h after exposure. - Concentrations of-the f irst two proteins decreased up to the end of the second week. The 53-k D protein could be detected in serum even on day 21 after the treatmen t. After exposure of rats to a carcinogen,:a significant increase in b lood levels of 64 and 53-kD proteins was found, The 64-kD protein accu mulated in DMH-treated tumor-free rats,whereas high blood levels of p5 3 protein were found in cancer-bearing rats. Conclusions - p53 protein should be considered as a protein related to pathological changes in the organism, i.e., as a stress response protein. The increased expres sion of this protein may be manifested-in different biological process es, including tumorigenesis and:inflammatory diseases. In such cases, the over-expression of p53 protein may Serve as a part of a cellular d efense mechanism which has developed as a reaction of the organism to stress.