Platonin, a cyanine photosensitizing dye, causes attenuation of circulatory shock, hypercoagulable state, and tissue ischemia during heat stroke.

The aim of this study was to investigate the therapeutic effect of platonin, a cyanine photosensitizing dye as well as an inhibitor of proinflammatory cytokines, in an animal model of heat stroke. Anesthetized rats, immediately after the onset of heat stroke, were divided into two major groups and given the following: normal saline (1 mL per kg body weight) intravenously, or platonin (12.5-50 microg/mL per kg body weight) intravenously. They were exposed to ambient temperature of 43 degrees C to induce heat stroke. Another group of rats was exposed to room temperature (26 degrees C) and used as normothermic controls. Their physiologic and biochemical parameters were continuously monitored. When the vehicle-treated rats underwent heat exposure, their survival time values were found to be 18 to 22 min. Resuscitation with intravenous doses of platonin, but not normal saline, immediately at the onset of heat stroke, significantly improved survival during heat stroke (41-147 min). All heat-stressed animals displayed systemic inflammation and activated coagulation, evidenced by increased tumor necrosis factor-alpha, prothrombin time, activated partial thromboplastin time, fibrinogen degradation products, and D-dimer, and decreased platelet count and protein C. Biochemical markers evidenced cellular ischemia and injury/dysfunction: plasma levels of blood urea nitrogen, creatinine, glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, and alkaline phosphatase, and striatal levels of partial pressure of oxygen, local cerebral blood flow, glycerol, glutamate, and lactate/pyruvate were all elevated during heat stroke. The systemic inflammation, hypercoagulable state, and cerebral ischemia and injury during heat stroke were all significantly suppressed by platonin. The data demonstrate that platonin therapy may resuscitate heat stroke victims by reducing circulatory shock, systemic inflammation, hypercoagulable state, and tissue ischemia and injury.