Previous work has shown that
2,3,7,8-tetrachlorodibenzo-p-dioxin (
TCDD) causes
porphyria, enhanced by
iron, in C57BL/6J mice with marked accumulation in the liver of
uroporphyrin I and III isomers and heptacarboxylic
acid III and is one model of human
porphyria cutanea tarda. Preliminary examination by HPLC also indicated the presence of some oxygenated side chain uroporphyrin derivatives. Here, the
porphyrin constituents of
TCDD-induced porphyric liver have been examined by HPLC/electrospray ionization quadrupole time-of-flight mass spectrometry (HPLC/ESI-Q-TOFMS) to characterize the major and minor
porphyrins present in hepatic tissue. As well as the major constituents
uroporphyrins I and III, we identified the isomers of heptacarboxylic, hexacarboxylic, and pentacarboxylic
acid porphyrins arising from intermediates in the stepwise decarboxylation of uroporphyrinogen I and III to
coproporphyrinogens. In addition, monohydroxy analogues of uroporphyrin isomers were detected hydroxylated in the
acetic acid and beta-positions of
propionic acid side chains and in the meso ring position. Of particular note, for the first time for human and experimental
porphyrias, we found chlorins (dihydroxy-, hydroxyspirolactone- ,and dihydroxyspirolactone-urochlorins) consistent with those derived from an epoxyurochlorin structure, formed by oxidation of the double bond of a
pyrrole ring of uroporphyrinogen I and III isomers. The findings demonstrate that
oxygen insertion into the
pyrrole rings of
uroporphyrinogens occurs under pathological circumstances in vivo and support the evidence for an oxidative cellular environment present in
TCDD-treated porphyric tissue.