Reticuloendothelial system (RES) clearance function correlates with the mortality rate associated with stresses that can induce shock. Likewise, experimental rat heat stress (ERHS) mortality rate is altered by modulation of RES function. Since plasma fibronectin (PF) in many instances appears to mediate in vivo phagocytosis by the RES, the relationship between mean plasma fibronectin level (MPFL) and ERHS mortality was examined. A comparison of MPFLs prior to ERHS revealed that rats which ultimately comprised the survival group had a MPFL of 269.0 +/- 11.2 micrograms/ml, whereas that of the nonsurvivors was 252.9 +/- 11.9 micrograms/ml. Both groups had elevated MPFLs up to 12 h following ERHS. However, after this time, MPFL began to decline. The decline was more severe for the nonsurvivors, with MPFLs at 15, 18, and 20.3 h significantly (P less than 0.01) lower than the values for the survival group. Even the lowest MPFL (256.0 +/- 30.7 micrograms/ml) noted for the survival group was still significantly (P less than 0.01) higher than the value (159.3 +/- 13.3 micrograms/ml) determined for agonal samples collected from nonsurvivors. Furthermore, grouping rats according to their preheat PF level demonstrated that rats with levels exceeding 300 micrograms/ml had significantly (P less than 0.05) reduced mortality rates (12.5 vs. 51.3%) compared with rats with levels below this value. It was concluded that elevated PF levels prior to ERHS correlated with thermotolerance.
Animals Fibronectins