title: Sorbent therapy of the porphyrias. V. Adsorption of the porphyrin precursors delta-aminolevulinic acid and porphobilinogen by sorbents in vitro.
abstract: The acute attacks of the acute hepatic porphyrias may be precipitated by the excessive intracellular accumulation of the porphyrin precursors delta-aminolevulinic acid (ALA) or porphobilinogen (PBG). Sorbents that bind porphyrin precursors in the gastrointestinal tract may interrupt their enterohepatic circulation, thus reducing the body burden of these materials and minimizing the frequency or severity of acute attacks. We have determined the adsorption capacities (Qm's) of several activated charcoals and the ion exchange resin cholestyramine for ALA and PBG. Qm's (mg ALA or PBG adsorbed/gm dry sorbent) were determined from Langmuir isotherms, which were derived from studies of the amount of porphyrin precursor adsorbed after the addition of a constant amount of ALA or PBG to varying amounts of sorbent. These experiments were carried out pH 8.2 in 0.1% desoxycholate, to simulate conditions of the small intestine. Extremely high Qm's were obtained for all charcoals and both porphyrin precursors; those for cholestyramine were one or several orders of magnitude lower. For ALA, the Qm of Gulf Bio-Systems Super Char charcoal (110 +/- 35 [SD]) was not significantly greater than that of Med-Corp Acta-Char charcoal (95 +/- 20), but it did exceed those of all other charcoals by a statistically significant amount. For PBG, the Qm of Super Char (68 +/- 14) was marginally greater than that of Mallinckrodt USP charcoal (42 +/- 21, t8 = 2.18, p approximately equal to 0.06), but it was significantly greater than that of Acta-Char charcoal (27 +/- 12). All sorbents adsorbed ALA or PBG at comparable rates, and the complex of sorbent and porphyrin precursor appeared to be undissociable.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000327:Adsorption; D000622:Aminolevulinic Acid; D002606:Charcoal; D002792:Cholestyramine Resin; D007700:Kinetics; D007982:Levulinic Acids; D011162:Porphobilinogen
chemical_list: D007982:Levulinic Acids; D002792:Cholestyramine Resin; D002606:Charcoal; D011162:Porphobilinogen; D000622:Aminolevulinic Acid