Evaluation of a rat model for the study of local regulation of intestinal blood flow: ex vivo asanguineous perfusion of the ileal vascular bed

Abstract

A new model of ex vivo vascularly perfused, isolated rat ileum was developed and evaluated. Segments of distal ileum (approximately 5 cm) from male Wistar rats were isolated on their vascular pedicles. Perfusion through an aortic cannula with oxygenated (95% O 2, 5% CO 2) Krebs solution containing 5% bovine albumin, 5.6 m M glucose, and 25 m M mannitol at 37°C was initiated immediately after interruption of blood flow. The bowel preparations, including the abdominal aorta, were then transferred to a perfusion chamber. Perfusion pressure was maintained by gravity at 40 mm Hg. Flow was measured with an electromagnetic flow probe. The portal vein, together with the lymphatics, drained freely into collection tubes. The bowel lumen was perfused at 0.85 ml/min with isotonic modified Krebs solution containing [ 14C]polyethylene glycol, and the luminal perfusion pressure was monitored. Luminal effluents were collected through a large-bore outlet tubing. As determined by histology, O 2 consumption, vascular reactivity, and mucosal permeability, the preparations were viable for at least 60 min of perfusion. With this model, a vasoconstrictor effect of the α 2-adrenoceptor agonist clonidine was documented for the first time in isolated rat bowel.