Cobalt-Mesoporphyrin Inhibits Heme Oxygenase Activity but It Does Not Induce Lipid Peroxidation in Rat Brain Membranes during Photoirradiation

Abstract

We examined the effects of cobalt-mesoporphyrin (CoMP) in vitro. The porphyrin inhibited the activity of rat splenic heme oxygenase but scarcely stimulated peroxidation of lipids in a membrane fraction from rat brain during photoirradiation. The apparent inhibition constant for CoMP was 344 nM. It is suggested that CoMP may be a promising candidate for a chemopreventive of neonatal hyperbilirubinemia that is not associated with phototoxicity.

Metal Complexes as Enzyme Inhibitors

“…54,55 Co-MP does not appear to mediate lipid peroxidation in rat brain membranes after photoirradiation (as determined by malondialdehyde assay), indicating that it does not act as a photosensitizer. 54 Cr-MP effectively inhibited hepatic HO after oral administration but not splenic HO. 55 Zn-MP has also been found to inhibit hepatic δ-aminolevulinate synthase (ALAS), the rate-limiting enzyme in the heme biosynthesis pathway, an effect which is enhanced when heme is added with the porphyrin.…”

“…Co−MP and Cr−MP have also demonstrated effective inhibition of HO. , Co−MP does not appear to mediate lipid peroxidation in rat brain membranes after photoirradiation (as determined by malondialdehyde assay), indicating that it does not act as a photosensitizer . Cr−MP effectively inhibited hepatic HO after oral administration but not splenic HO .…”