Pitfalls using metalloporphyrins in carbon monoxide research

The proposal that endogenously produced carbon monoxide (CO) may act as a biological messenger has remained controversial. Carbon monoxide is generated by haem oxygenase isoenzymes in the degradation of haem-containing molecules. Certain metalloporphyrins, which are inhibitors of haem oxygenase, have been widely used as pharmacological tools in order to establish a messenger role for CO in the brain and periphery. However, increasing evidence shows that many metalloporphyrins are also associated with a large range of undesired effects, which make the interpretation of results using such compounds very uncertain. In this article, Lars Grundemar and Lars Ny evaluate the properties and describe the nonselective effect profile of such metalloporphyrins.