A rat model for studying the intestinal circulation.

A preparation is described that allows for whole-organ studies on the rat intestinal microcirculation. The preparation is an in situ autoperfused segment of small intestine. An arterial perfusion circuit is established between the carotid and superior mesenteric arteries and a venous circuit between the superior mesenteric and jugular veins. This model allows for measurements of superior mesenteric arterial and venous pressures, blood flow, arteriovenous oxygen difference, lymph flow, capillary pressure, capillary reflection coefficient, and the capillary filtration coefficient. Preliminary studies using this model indicate a resting blood flow of approximately 120 ml X min-1 X 100 g-1. Resting intestinal oxygen consumption is approximately two to three times the value reported for dogs and cats. Experiments were performed to assess the responses of the preparation to commonly employed physiological perturbations, including pressure-flow autoregulation, functional hyperemia, and response to venous pressure elevations. The observed responses are consistent with intrinsic control of resistance and exchange vessels. The model should prove useful for future studies regarding the physiology and pathology of intestinal hemodynamics, oxygenation, and capillary fluid exchange.