Comparative Study of Protoporphyrins in Erythropoietic Protoporphyria and Griseofulvin-Induced Murine Protoporphyria

Abstract

A B S T R A C T Excess erythrocyte protoporphyrins of human congenital erythropoietic protoporphyria and of griseofulvin-induced murine hepatic protoporphyria were found to be associated with hemoglobin and stroma fractions in similar relationships. More than 99.5% of total erythrocyte protoporphyrin was bound to hemoglobin in each case. However, profound differences were found when protoporphyrin concentration was measured in erythrocytes that had been segregated into populations of progressive age on discontinuous density gradients. In erythropoietic protoporphyria, porphyrin content diminished rapidly with age; in murine protoporphyria, the aging erythrocyte populations became progressively more porphyrin rich. In vitro diffusion of protoporphyrin from plasma across the intact erythrocyte membrane was demonstrated. The equimolar binding affinity of protoporphyrin to hemoglobin was shown to be 40 times that of protoporphyrin to serum albumin. This strong affinity provides the driving force for the observed transmembrane diffusion, and explains the high erythrocyte/plasma porphyrin ratio in murine hepatic protoporphyria. The opposite rapid efflux of intraerythrocytic protoporphyrin into plasma previously shown in uncomplicated erythropoietic protoporphyria occurs despite this strong hemoglobin affinity, implying continuous efficient clearance of protoporphyrin from plasma by the liver. Furthermore, these and other This work was presented in part at the 7th International Congress on Photobiology, Rome, Italy, September, 1976. Received for publication 22 November 1976 and in revised form 29 March 1977. data suggest that a hepatic synthetic source for any significant fraction of the blood protoporphyrin in erythropoietic protoporphyria is highly improbable. INTRODUCTION Congenital protoporphyria in humans was first named erythropoietic protoporphyria (EPP)' (1-3) based upon the large amounts of protoporphyrin IX (PP) found in the blood of patients with the disease which was thought to be synthesized in the bone marrow. However, the observation was made that the daily excretion of PP in the feces of these patients approached the total excess PP in the circulating erythrocyte mass. It was clear that this amount could not be derived from senescent erythrocytes only (4). Some investigators proposed the liver as an important additional source of PP in this disease. Acquired protoporphyria is extremely rare in man, but protoporphyria can be easily induced in mice with certain drugs, among which is griseofulvin (GF) (9-11). Murine protoporphyria induced by oral administration of GF has been used as an experimental model for human EPP (12,13). The site of excess PP synthesis in GF-induced murine protoporphyria (GFPP) is thought to be primarily, if not solely, hepatic (14). However, the concentration of PP associated with the circulating erythrocytes in GFPP can become comparable to that observed in EPP (9, 13, 14).We have developed spectrofluorometric techniques which give information about the binding sites of PP ...

Light-induced protoporphyrin release from erythrocytes in erythropoietic protoporphyria.

“…After equilibration for 24 h, the released protoporphyrin redistributes and is bound to hemoglobin if hemoglobin is released in sufficient amounts. The redistribution of protoporphyrin to hemoglobin is concentration dependent and takes place if the albumin concentration is <40 times the hemoglobin concentration (27). The concentration of albumin here is 15 ,gM and of hemoglobin 3.4 ,M (8% hemolysis after 240 kJ/m2).…”

Protoporphyrin-induced Cholestasis in the Isolated In Situ Perfused Rat Liver

“…Liver disease with histopathology resembling that seen in patients with protoporphyria has been produced by administering porphyrinogenic agents, e.g., griseofrilvin, to mice (20)(21)(22). Unfortunately this has not proved particularly valuable in addressing the nature of protoporphyrin deposition in the liver as it applies to cases of protoporphyria in htumans (23), except in cases in which the liver is primarily responsible for protoporphyrin overproduction (24). The recent demonstration of a bovine form of protoporphyria may provide a more meaningful model to clarify many aspects of the disorder (25).…”

Autofluorescence of Condensed Heme Aggregates in Malaria Pigment and Its Synthetic Equivalent Hematin Anhydride (β-Hematin)

“…51,52 Their fluorescence is such that only a minute amount can generate a detectable signal in solution. 26,53,54,56 This was demonstrated here in very dilute hemin solutions as fluorescence PPIX peaks appeared in 10 µM hemin. ( Figure 5A) In the condensed phase, fluorescence from PPIX and HA have quite different signatures ( Figure 6B-D).…”