Chylomicrons were separated from lymph collected from thoracic duct-cannulated rats receiving 20 mg 9,10-dimethyl-l,2-benzanthracene (DM BA) and 25 MCi DMBA-9-14C intragastrically. In order to ascertain the moiety of the chylomicron with which DMBA is associated, the chylomicrons were disrupted by freeze-thawing and subjected to chromatography and autoradiography. These procedures showed that the lipophilic DMBA molecule remains dis solved in the lipid fraction of the chylomicron. In another

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... dy, animals were divided into three groups and each rat was given hourly i.v. injections of either 0.9% NaCl solution, 1.0 mg protamine sulfate, or 25 USP units of heparin in a volume of 0.25 ml. Injections were begun 1 hr prior to and continued for 5 hr following the administration of 20 mg DM BA and 25 MCiDM BA-9-14C.DM BA uptake by mammary parenchymal cells of rats receiving either protamine or heparin was similar. However, in both groups, the parenchymal cell uptake of DMBA was significantly less than that of rats given injections of 0.9% NaCl solution. Although heparin was effective in promoting chylomicron lysis, it is apparent that this compound has an additional action. This effect of heparin upon DMBA uptake by mammary gland parenchymal cells may be occurring at the membrane of either the arterial endothelial cell and/or mammary parenchymal cell. These data do indicate that the majority of the DMBA taken up by the mammary gland parenchymal cells is mediated through transport in chylomicrons.