Tissue hypoxia indicators after severe controlled hemorrhage in inbred rat strains

Abstract

Eight-fold differences in survival time were detected among 15 inbred rat strains after a controlled hemorrhage (Klemcke et al., FASEB J 20: , 2006). To assess potential mechanisms of these differences, indicators of tissue hypoxia (lactate, pH, bicarbonate [HCO3], and base deficit [BD]) were measured in arterial blood at the beginning (basal) and end (final) of hemorrhage. Rats were catheterized and, 24 hours later, 55% of the blood volume was removed during a 26 min period from conscious unrestrained animals. Rats were then observed for 6 hr or until death. Using average values for each strain, there were correlations (P <0 .01) between survival time and final lactate (r=−0.86), HCO3 (r=0.88), and BD (r=−0.87), whereas associations between final pH and survival time were weak (r=0.5; P=0.05). There were no correlations between basal levels and survival time (P ≥0.16). In support of these correlations, analysis of all strains via ANOVA revealed that longer-lived strains had lower (P<0.01) final lactate and BD values, but higher (P<0.01) final HCO3 than strains with shorter survival times. Therefore, inbred rat strains demonstrate early differences in their ability to maintain aerobic metabolism that relate to their ability to survive severe hemorrhage.