Portal and systemic plasma lipopolysaccharide concentrations in heat-stressed primates

Lipopolysaccharide (LPS) concentrations in hepatic portal and systemic arterial plasma were determined in five anesthetised monkeys heat-stressed by an environmental temperature of 41.0 +/- 0.3 degrees C and 100% relative humidity. As the rectal temperature (Tr) rose, the LPS concentrations in both the portal and systemic arterial plasma remained at the pre-heat-stress levels of 0.088 +/- 0.017 and 0.078 +/- 0.021 ng/ml (N.S.), respectively, until a Tr of 42.5-43.0 degrees C, when the LPS concentration increased slowly, first in the portal plasma and then in the systemic plasma. On the other hand, the concentration of plasma anti-LPS IgG antibodies began to decline at temperatures as low as 40 degrees C from 20.66 +/- 7.35 micrograms/ml (portal) and 22.14 +/- 7.43 micrograms/ml (arterial) to 5.51 +/- 1.28 micrograms/ml (portal) (P less than .05) and 4.6 +/- 1.69 micrograms/ml (arterial) (P less than .05) just prior to death. Above a Tr of 43 degrees C, the LPS concentration increased rapidly to a maximum of 0.244 +/- 0.05 ng/ml (portal) (P less than .01) and 0.224 +/- 0.06 ng/ml (arterial) (P less than .01). The mean arterial pressure remained more or less constant at 112 +/- 17.03 mm Hg until a Tr of 41.5 degrees C and then rapidly declined as Tr rose (P less than .01). The heart rate rose gradually from 154 +/- 14 min-1 as Tr increased and then rapidly after a Tr of 41.5 degrees C to a maximum of 307 +/- 13 min-1 at 43.0 degrees C. Thereafter it declined rapidly until death.(ABSTRACT TRUNCATED AT 250 WORDS)