The porphyrias are a group of disorders of haem biosynthesis in which overproduction of haem precursors is associated with characteristic clinical features. Two main forms of clinical manifestation may occur together or separately: lifethreatening attacks of acute porphyria and photosensitization of the skin. • Because the porphyrias may present in ways that mimic other disorders, and because different types of porphyria share identical clinical features, accurate diagnosis depends on identifying patterns of haem precursor overproduction. This requires correct selection, performance and interpretation

https://journals.sagepub.com/doi/pdf/10.1177/000456329002700501

Laboratory investigation of the porphyrias.

Different cell lines were given photodynamic treatment with 5-aminolaevulinic acid (ALA) and light. In addition, the iron chelator 1,2-diethyl-3-hydroxypyridin-4-one (CP94) was used. The porphyrin species produced was spectrofluorimetrically identified as protoporphyrin IX. All the cell lines responded to treatment, including a multidrug resistance gene expressing bladder cancer line and, to a lesser degree, cells derived from untransformed human skin fibroblasts. CP94 enhanced both porphyrin fluorescence, total porphyrin content and photosensitivity of the cells. CCD fluorescence microscopy showed a granular extranuclear porphyrin fluorescence distribution for all the cell lines involved, but the untransformed cells showed a distribution pattern different from the ones seen in the other cells.

A hydroxypyridinone (CP94) enhances protoporphyrin IX formation in 5-aminolaevulinic acid treated cells.

Numerous studies during the past several decades have demonstrated that porphyrins and other constituents of the heme biosynthetic pathway might serve as sensitive and specific biomarkers of toxic metal exposures in human subjects. Porphyrins (in the reduced form, porphyrinogens) are formed as intermediates of heme biosynthesis in essentially all eukaryotic tissues and are readily measured following extraction in the oxidized form (porphyrins) in blood cells, urine, feces, and other accessible tissues. The utility of porphyrins as biomarkers of metal exposures is based largely on the properties of metals to selectively alter porphyrinogen metabolism in target tissues by mechanisms which lead to metal-specific changes in urinary porphyrin excretion patterns. Of particular importance with respect to the utility of porphyrins as biomarkers of metal effects in target tissues is the property of some specific metals, not only to impair porphyrin(ogen) metabolism, but also to facilitate the oxidation of reduced porphyrins which subsequently accumulate in tissue cells. Evidence indicates that the pro-oxidant action of metals which promotes porphyrinogen oxidation may also underlie the oxidation of other cellular constituents, such as lipids and proteins, a postulated cause of cell injury. Hence, a common mechanistic etiology underlying the porphyrinogenic and tissue-damaging properties of metals provides the rationale for use of porphyrin measurements as an indicator of metal exposure as well as potential toxicity.

Porphyrin Metabolism as Indicator of Metal Exposure and Toxicity

https://www.journal-of-hepatology.eu/article/S0168-8278(09)00587-X/pdf

Porphobilinogen deaminase over-expression in hepatocytes, but not in erythrocytes, prevents accumulation of toxic porphyrin precursors in a mouse model of acute intermittent porphyria

Simultaneous determination of six urinary porphyrins using liquid chromatography-tandem mass spectrometry.

We describe a fluorescence method for screening and quantifying urinary porphyrins. New and effective approaches are used to oxidize prophyrinogens, correct the baseline, and ensure that uroporphyrin (uro) and coproporphyrin (copro) are equally detected, mole for mole. No preliminary purification is required. A 45-microL aliquot of urine is oxidized with 3 mmol/L iodine in 3 mol/L HCl to convert porphyrinogens to porphyrins, and then decolorized with 5 mL of 0.45 mmol/L sodium thiosulfate. An excitation scan is done from 350 nm to 440 nm, monitoring emission at 650 nm. Total porphyrin content is determined at the isosbestic point for uro and copro, and the mole fractions of uro and copro are estimated from the wavelength of the signal maximum. There is no interference from protein, glucose, bilirubin, or hemoglobin in high concentration. The limit of detection is less than 30 nmol/L and linearity is maintained up to 3200 nmol/L. Recoveries and precision are excellent. This is a rapid, sensitive screen for porphyrinuria as well as an accurate and precise quantitative method. We compared the method with existing methods and discuss some shortcomings common to many of them.

A rapid and accurate spectrofluorometric method for quantification and screening of urinary porphyrins.

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A rapid and accurate spectrofluorometric method for quantification and screening of urinary porphyrins.