Cold cardioplegic arrest enhances heat shock protein 70 in the heat-shocked rat heart

The proarrhythmic effects of hypothermia in atria isolated from 5-HT4-receptor-overexpressing mice

We investigated whether hypothermia would be arrhythmogenic in mice that overexpress the human 5-HT₄ receptor only in their cardiac myocytes (5-HT₄-TG). Contractile studies were performed in isolated, electrically driven (1 Hz) left and spontaneously beating right atrial preparations of 5-HT₄-TG and littermate wild-type control mice (WT). Hypothermia (23 °C) decreased the force of contraction in the mouse right and left atrial preparations. Moreover, the concentration-dependent positive inotropic effects of 5-HT were blunted but still shifted to lower 5-HT concentrations in the left 5-HT₄-TG atria in hypothermia compared to normothermia (37 °C). Furthermore, hypothermia increased the incidence of right atrial arrhythmias in 5-HT₄-TG more than in WT mice. In contrast, at 37 °C, lowering the potassium concentration from 5.2 to 2.0 mM also induced arrhythmias in the right atrium, but with a similar incidence in WT and 5-HT₄-TG mice. In contrast, 10 μM d,l-sotalol and 300 μM erythromycin did not induce arrhythmias. Hypothermia was accompanied by the increased expression of heat shock protein 70 (HSP70) in WT but not in 5-HT₄-TG mice. We concluded that without the stimulation of 5-HT₄-receptors by exogenous agonists, a simple temperature reduction can increase arrhythmias in 5-HT₄-TG mice. It is tempting to speculate that in human patients, 5-HT₄ receptors might contribute to potentially deadly hypothermia-induced arrhythmias.

Heat Shock Proteins: Protection and Potential Biomarkers for Ischemic Injury of Cardiomyocytes After Surgery

The heat shock proteins are endogenous proteins with the ability to act as molecular chaperones. Methods that provide cell protection by way of some damage can positively influence the results of surgery. The present review summarizes current knowledge concerning the cardioprotective role of the heat shock proteins as occurs in heart damage, including relevant information about the stresses that regulate the expression of these proteins and their potential role as biomarkers of heart disease.

Relationship between pulmonary fat embolism and core body temperature in rats with a severe fatty liver

We previously demonstrated that pulmonary fat embolism was induced by elevation of the core body temperature, in rats with a fatty liver. The aim of the present examination was to investigate the core body temperature at which pulmonary fat embolism developed capillaries through exposure to a high temperature, in rats with a fatty liver. Following heat stress, pulmonary fat embolism was observed to a slight degree at a core body temperature of 41 and 42 degrees C, whereas the severity of pulmonary fat embolism was greatly increased and was classified as severe at a core body temperature of 43 degrees C. Moreover, the concentrations of aspartate aminotransferase and alanine aminotransferase within plasma were significantly increased at a core body temperature of 43 degrees C. These results clearly indicate that the development of pulmonary fat embolism could be related to hyperthermia at above 42 degrees C following heat stress, and that fat emboli may be derived from the fatty liver itself. It is thus likely that pulmonary fat embolism can be considered as one form of evidence of hyperthermia in an individual with a fatty liver.