Prophylactic corticosteroid suppresses endotoxemia in heat-stressed primates

We previously found that lipopolysaccharides (LPS) leak from the gut lumen into the hepatic portal vein during heat stroke. Furthermore, we found that prophylactic corticosteroid administration could prevent a rise in plasma LPS concentration in superior mesenteric artery occlusion shock. In this study, we found that treatment prior to heat-stress with corticosteroids could prevent any rise in plasma LPS concentration in heat-stressed primates. Two groups of primates, one of which received a prophylactic dose of methylprednisolone sodium succinate (MPSS) (n = 4) were subjected to heat-stress (41 +/- 0.3 degrees C). Their arterial blood pressure, heart rate and rectal temperature (Tr) were continuously recorded. In the untreated control group (n = 8), the plasma LPS concentration tended to increase slowly at a Tr of 41.5 degrees C from an initial 0.06 +/- 0.013 ng.ml-1. Above a Tr of 43 degrees C, the plasma LPS level rose rapidly until at a Tr of 44.4 +/- 0.1 degrees C, the mean LPS level was 0.315 +/- 0.03 ng.ml-1 (p less than 0.001). Prophylactic treatment with MPSS suppressed the increase in plasma LPS levels to 0.066 +/- 0.01 ng.ml-1 before heat-stress and 0.03 +/- 0.01 ng.ml-1 at Tr 44.4 degrees C just before primate demise. The mean arterial pressure of the control group was lower than the treated group for any given Tr; between Tr 42-43 degrees this difference was significant (p less than 0.05). Moreover, the cardiovascular parameters began to deteriorate at a lower Tr in the control group.