CHARACTERIZATION OF COLD-INDUCED HEAT-SHOCK-PROTEIN EXPRESSION IN NEONATAL RAT CARDIOMYOCYTES

Cardiac surgery is usually performed under conditions of cardioplegic ischemic arrest. To protect the heart during the ischemic period, the myocardium is exposed to varying degrees of hypothermia. Although hype rthermia is known to induce the heat shock response, the molecular eff ects of hypothermia on the myocardium have not been investigated. We h ave studied the effect of hypothermia on the induction of heat shock p roteins in primary cultures of neonatal cardiomyocytes. Cold stress in cardiomyocytes induced a 6 fold increase in the heat shock protein HS P70 as compared to control. Increased HSP70 protein levels correlated with induction of HSP70 mRNAs. Maximal levels of HSP70 protein appeare d 4-6 h following recovery from cold shock, indicating the transient n ature of the response. Induction of HSP25 mRNA was also observed in co ld-shocked cardiomyocytes, even though increased HSP25 protein levels were not detected. Our results indicate that hypothermia is capable of inducing the heat shock response in neonatal cardiomyocytes.