Recombinant human erythropoietin improves gut barrier function in a hemorrhagic shock and resuscitation rat model.

BACKGROUND: Gut injury and bacterial translocation develop and persist after limited periods of hemorrhagic shock. Erythropoietin (EPO) can exert hemodynamic, anti-inflammatory, and tissue protective effects. We tested the hypothesis that EPO given at the time of resuscitation with saline will reduce functional ileal injury 24 hours after shock. METHODS: Sprague-Dawley rats (n = 6 per group) were randomized to sham surgery or hemorrhagic shock maintained at mean arterial pressure 40 mm Hg for 60 minutes and then treated with either saline resuscitation (three times the volume of shed blood) or saline + recombinant human EPO (rHuEPO) resuscitation. Intravenous rHuEPO (1,000 U/kg) was given at the start of saline resuscitation, and at 24 hours ileal function was evaluated using quantitative cultures of mesenteric lymph nodes to assess for bacterial translocation (colony-forming units per gram of tissue [CFU/g]), determination of portal vein plasma endotoxin levels and histopathological evaluation using semi-thin plastic sections of the distal ileum. In a second series of animals, fluorescein isothiocyanate-dextran 4000 (FD-4) was used to assess mucosal permeability of the distal ileum to macromolecules. RESULTS: At 24 hours, the saline group had morphologic evidence of intestinal injury when compared with the sham group, and the degree of mucosal injury was less in the saline + rHuEPO when compared with the saline group, which demonstrated significantly reduced bacterial translocation to the mesenteric lymph nodes (383 CFU/g ± 111 CFU/g vs. 1130 CFU/g ± 297 CFU/g; p < 0.05) and decreased terminal ileum permeability to FD-4 (3.08 µg/mL ± 0.31 µg/mL vs. 5.14 µg/mL ± 0.88 µg/mL; p < 0.05). No significant difference was found in the portal vein endotoxin levels between the two groups. Histopathological evaluation demonstrated a trend for decreased enterocyte disarray or disruption and vacuolization in the saline + rHuEPO versus saline group. CONCLUSION: Using rHuEPO at time of saline resuscitation resulted in decreased bacterial translocation and permeability to macromolecules 24 hours after shock. These observations suggest that rHuEPO can mediate a protective effect on intestinal mucosal barrier function during ischemic injury.

Atomic force microscopy analysis of rat pulmonary surfactant films.

Pulmonary surfactant facilitates breathing by forming a surface tension reducing film at the air-liquid interface of the alveoli. The objective was to characterize the structure of surfactant films using endogenous rat surfactant. Solid-support surfactant films, at different surface pressures, were obtained using a Langmuir balance and were analyzed using atomic force microscopy. The results showed a lipid film structure with three distinct phases: liquid expanded, liquid ordered and liquid condensed. The area covered by the liquid condensed domains increased as surface pressure increased. The presence of liquid ordered phase within these structures correlated with the cholesterol content. At a surface pressure of 50 mN/m, stacks of bilayers appeared. Several structural details of these films differ from previous observations made with goat and exogenous surfactants. Overall, the data indicate that surfactant films demonstrate phase separation at low surface pressures and multilayer formation at higher pressure, features likely important for normal surfactant function.