Lymphatic appearance of DDT in thoracic or mesenteric lymph duct cannulated rats

Lymphatic absorption studies were conducted in rats using DDT (2,2-bis(P-chlorophenyl)1,1,1-trichloroethane; p,p-DDT) as a lymphatically absorbed model compound. The lymphatic appearance of DDT in either mesenteric or thoracic duct fistulated rats was followed after oral administration of 2 mg DDT in oleic acid (200 μl) per rat or intravenous administration of l mg DDT in Intralipid per rat. For the oral studies, 2 differing protocols were followed that were concerned with evaluating the effect of the timing of lymph duct cannulations on the subsequent lymphatic transport of DDT. The results of the study confirm that the lymphatic route is an important pathway for DDT absorption following oral dosing. Thoracic lymph was found to contain DDT absorbed directly into the lymph via the mesenteric lymph duct, as well as DDT absorbed via other routes, presumably portal blood. Significant amounts of DDT appeared in thoracic lymph following oral administration, even when the mesenteric lymph duct was occluded. Moreover, after intravenous administration, higher quantities of DDT appeared in thoracic lymph (3.6% of dose/24 h) than in mesenteric lymph (0.6% of dose/24 h). It appears, therefore, that collection of thoracic lymph overestimates the extent of direct intestinal lymphatic absorption of DDT after oral administration. The timing of the lymph duct cannulation with respect to the fasted state of the animal appears to effect the rate and extent of lymphatic absorption of orally administered DDT.