MAGNETIC-RESONANCE-IMAGING OF THE HEPATOBILIARY SYSTEM - INTESTINAL-ABSORPTION STUDIES OF MANGANESE MESOPORPHYRIN

Rationale and Objectives. We studied the intestinal absorption of mang anese mesoporphyrin (Mn-mesoporphyrin), a potential oral hepatobiliary contrast agent.Methods. Mn-mesoporphyrin was complexed with monoolein and taurocholate (mixed micelles). Portal venous delivery and biliary excretion were measured after intestinal administration in rats and r abbits, and the mechanism of intestinal transport was studied in a com bined lymph-bile fistula model in rats. T1-weighted magnetic resonance (MR) images of the liver were obtained in rats and domestic pigs befo re and after gastric administration of Mn-mesoporphyrin in mixed micel les. Results. A 2.2-fold increase of portal venous Mn con centration w as found 90 min after intestinal administration of the complex. None w as found in the lymph collected from the thoracic duct, indicating a t ranscellular transport mechanism through the intestinal mucosa with po rtal venous delivery. Mn-mesoporphyrin levels in bile peaked bem een 2 40 and 270 min after administration (200-fold increase). The greatest liver enhancement (20-90%) was measured 360 min after administration. Conclusion. The feasibility of intestinal delivery of Mn-mesoporphyrin , a lipophilic hepatobiliary contrast agent, was demonstrated.