Immunoexpression of HSP27 and HSP70 after hyperthermia in postnatal rat lung and heart.

This study aimed to investigate the changes in HSP27 and HSP70 immunoexpression after hyperthermia in the lung and heart of rats on days 5, 10, 20, 25, and 30 of postnatal development. The body temperature of rat pups in the hyperthermia groups was increased to 40°C under the infrared lamp. The recovery time after hyperthermia was kept at 5 hours. HSP27 was present in cardiomyocytes and bronchiole and alveolar epithelial cells of control rats. Compared to the control groups after hyperthermia, HSP27 expression was only significantly different on day PND10 for cardiomyocyte cells (P < 0.05), but not on any day of postnatal development for bronchiole and alveolar epithelial cells (P > 0.05). In control group rats, HSP70 was almost absent in cardiomyocytes and alveolar epithelial cells but was evident in bronchiole epithelial cells. A significant increase in HSP70 expression after hyperthermia was observed throughout the postnatal days in cardiomyocytes and alveolar epithelial cells, but only on day PND20 in bronchiole epithelial cells (P < 0.05). In conclusion, during postnatal development, HSP27 is essential for the development of cardiomyocytes and bronchiole and alveolar epithelial cells, and HSP70 is essential for the development of bronchiole epithelial cells. On the other hand, HSP70 may participate in cytoprotective and repair mechanisms against hyperthermia-induced stress in cardiomyocytes and alveolar epithelial cells during postnatal development.