Chronic Collection of Mesenteric Lymph From Conscious, Tethered Rats

Previously reported methods for collecting lymph from the rat require total restraint of the animal and fluid replacement, by intravenous or intraduodenal infusion, to maintain lymph output. We developed a rat model to allow collection of mesenteric lymph for several days from conscious, minimally restrained animals. This model obviates the need for total restraint or general anesthesia, both of which are known to influence intestinal lymphatic transport of test compounds in unpredictable ways. Animals are provided free access to an electrolyte solution, which they consume in sufficient quantity to maintain excellent lymph output without the need for the previously required infusions for fluid replacement. Intestinal lymph flow rate during the first 24 hours after surgery averaged 2.23 (61.01) mL/hr, increasing to 4.89 (61.64) mL/hr thereafter. This flow rate is considerably greater than that previously described for methods requiring anesthesia or restraint of the animals. Using our model, we have successfully maintained lymph collection from cannulated rats for up to 5 days, with fully patent cannulae and no gross signs of physical distress.