INTESTINAL-ABSORPTION OF MN-MESOPORPHYRIN IN A SMALL-BOWEL SAC SYSTEM- EFFECT OF OLEIC-ACID

Rationale and Objectives. The authors investigated the effect of oleic acid (cis-9-octadecenoic acid) (OA), a lipidic carrier, on the intest inal absorption rate and T1 relaxation time of manganese (III) mesopor phyrin (Mn-mesoporphyrin), a prototype hepatobiliary contrast agent fo r magnetic resonance imaging. Methods. Mn-mesoporphyrin was formulated with OA at various concentrations. Small bowel sacs were created in 3 6 rats and filled with complexed and free Mn-mesoporphyrin. Intestinal absorption of Mn-mesoporphyrin was measured with spectrophotometry at 364 nm. T1 relaxation times were measured in samples of Mn-mesoporphy rin solutions, bowel wall, Liver, and bile. Results. Absorption rates ranged from 4.2%/cm(2)/h to 13%/cm(2)/h. Absorption was greatest (13%/ cm(2)/h) when a combination of 1 mmol/L. Mn-mesoporphyrin and 26.5 mmo l/L OA was used. The T1 of bile decreased from 2,480 to 248 msec (maxi mum decrease) in rats that received Mn-mesoporphyrin. Conclusion. Mn-m esoporphyrin is absorbed from the small bowel in both the lipid-associ ated and free form, resulting in substantial shortening of the T1 in b ile.