Cooling therapy upregulates protein C activation in heat stressed rats: An experimental study

Protein C (PC) pathway homeostasis is implicated in heat stress (HS). This study determines whether cooling could improve the PC pathway in HS. Fifty-six anesthetized rats were warmed to achieve HS (rectal temperature [Tr] 42°C). These rats were divided into seven groups: (a) control group:sacrifice immediately 15 min after HS; (b) HS+I:sacrifice immediately after 15 min ice-water treatment or (c) 3 hr after HS; (d) HS+C:sacrifice immediately after 15-min cold-water treatment or (e) 3 hr after HS; (f) HS: sacrifice immediately 15 min after HS or (g) 3 hr after HS. Plasma PC, activated protein C (APC), and soluble thrombomodulin (sTM) levels were tested at both time points. After cooling, Tr in the HS+I and HS+C groups significantly decreased, when compared with the HS group, and Tr was significantly lower in the HS+I group than in the HS+C group ( p < 0.05). Furthermore, sTM levels were highest in the HS group among the groups at both time points. Plasma PC and APC levels increased after HS. In the HS+I and HS+C groups, plasma APC levels and the APC/PC ratio significantly increased at both time points. The proportions were significantly higher in the HS+I group than in the HS+C group, and there was no significant increase in APC/PC ratio in the HS group. Cooling exerts an anticoagulant effect following HS by increasing APC levels. Ice-water blanket therapy is more effective than cold-water blanket therapy in increasing APC levels.