Cellular Signal Level of Cyclic AMP and Functional Integrity of the Small Bowel after Ischemic Preservation: An Experimental Pilot Study in the Rat

Abstract

The intestinal mucosa is one of the tissues most sensitive to ischemia. Anoxia of the gut is known to result in an early impairment of cellular permeability and transcapillary barrier function upon reperfusion. In vitro, an increased permeability of endothelial cell monolayers could be shown to be related to a decrese in cellular content of cyclic AMP (cAMP). Thus, the present study was aimed at investigating the role of the cellular cAMP second messenger signal in the context of intestinal ischemia/reperfusion injury after cold preservation. Segments of the upper jejunum were isolated from Wistar rats with vascular pedicle and flushed with 10 ml of UW preservation solution. The intestinal lumen was rinsed with 10–15 ml of UW solution and the organ was stored immersed in UW solution at 4°C for 4 or 18 h. After 18 h of cold ischemic storage structural and functional integrity of the preparation was tested by perfusion via the vascular system with modified Krebs-Henseleit buffer and the intestinal lumen with saline solution (containing 200 mg % of galactose) for 30 min. In half of the experiments, dibutyryl-cAMP a membrane permeable cAMP analogue, was admixed to the flush solution (2 mM). It was found that tissue levels of cAMP linearily decreased to 34% during 18 h of ischemic preservation in UW. Addition of dibutyryl cAMP significantly improved postischemic recovery of the intestinal preparations by decreasing cellular loss of lactic dehydrogenase (18.2 ± 4.6 vs. 7.6 ± 2.6 U/I) and improving intestinal absorbtion of galactose from the luminal circuit (0.18 ± 0.14 vs. 0.36 ± 0.14 mg %) after 30 min of oxygenated reperfusion, but was not effective to reduce transcapillary water loss into the gut lumen. It is concluded that the anoxia-related decrease of the cellular cAMP level may represent a codeterminator influencing postischemic recovery of the small bowel and that the control of the cAMP signal of ischemic intestines might improve the quality of cold preservation of the gut prior to transplantation.