BILIARY-EXCRETION OF PYRROLIC METABOLITES OF [C-14] MONOCROTALINE IN THE RAT

The biliary excretion of amphoteric pyrroles was studied using in situ isolated rat liver preparations perfused in a recirculatory manner fo r 60 to 90 min with C-14-monocrotaline (40 mu mol/120 ml of Krebs-Hens eleit buffer). After 90 min, 20% of the administered C-14 and an amoun t of pyrrole equivalent to 9 mu mol of dehydroretronecine was recovere d in the bile. Bile collected between 15 and 30 min contained the high est levels of C-14 and pyrrolic metabolites. Isoelectric focusing (IEF ) and electrophoretic separations on matrices of polyacrylamide and si lica were used to isolate and estimate levels of pyrrolic conjugates. IEF and electrophoretic separations on silica revealed the presence of six pyrrole-positive metabolites. Reactions of monocrotaline pyrrole with glutathione produced three conjugates that had the same pi values as components found in bile. Electrophoretic separations on silica an d polyacrylamide followed by reversed phase chromatography removed suf ficient biliary matrix contaminants to permit identification of glutat hione and cysteinyl-glycine conjugates of 7-dihydro-7-hydroxy-1-hydrox ymethyl-5H-pyrrolizine end 1-formyl-7-hydroxy-6,7-dihydro-5H-pyrrolizi ne with fast atom bombardment MS/MS. This study revealed a complexity in the biliary pyrrolic excretion profile that had not previously been realized.