Hemorrhage and renal ischemia-reperfusion upregulates the epidermal growth factor receptor in rabbit duodenum

To study the role of EGF-R in small intestinal adaptation to hemorrhage and I/R, anesthetized rabbits were implanted aseptically with arterial and venous catheters and bilateral renal artery Doppler flow probes and silastic occluders and allowed to recover. Rabbits were then randomly assigned to one of six groups: time control; hemorrhage (22.5 mL/kg) and 2.5 hours of renal occlusion (hemorrhage plus I/R); hemorrhage plus I/R and 2:1 LRS resuscitation; hemorrhage plus I/R and 3:1 LRS resuscitation; hemorrhage alone; or I/R alone. Rabbits were killed 48 hours after hemorrhage, and a section of duodenum was collected for analysis. Hemorrhage plus I/R induced a 2.5-fold increase in EGF-R tyrosine kinase activity compared with that found in the control group (P < .05), and this effect was not modified by either LRS resuscitation regimen. This increased activity was associated with similar Increases in EGF-R protein concentrations and approximately a 50% increase in EGF-R messenger (m)RNA levels compared with levels found in the control group. Further analysis of possible regulatory mechanisms for the increased EGF-R expression after hemorrhage plus I/R detected higher levels of EGF-R phosphorylation compared with those found in the control group but no significant increases in transforming growth factor-alpha mRNA levels. These data, coupled with a significant increase in duodenal thlobarbituric acid-reactive substance concentrations from rabbits in the hemorrhage plus I/R group, support the hypothesis that tyrosine kinase signal transduction pathways involving the EGF-R are activated in the small intestine after hemorrhage, renal I/R, or both, and this process may be mediated, at least in part, by oxidant stress.