Differential Modification of Hemoglobin Chains by Acetaldehyde

Abstract

Acetaldehyde-hemoglobin adducts have been suggested as potential markers for alcohol consumption. These adducts were formed in vitro with [¹⁴C]acetaldehyde and separated into hemoglobin subunits by cation-exchange chromatography to examine the relative modification of the α- and β-chains. The effect of varying concentrations of acetaldehyde on the relative amounts of polypeptide adducts and on the specific radioactivities of undissociated hemoglobin (Hb) following reaction with hydroxymercurybenzoate (HMB) was also studied. There were linear relationships (P < 0.05) between increasing levels of [¹⁴C]acetaldehyde (0.0, 0.1, 0.2, 0.5 mM) and the radioactivities of the α- and one of the two β-chain adducts (22, 25, 53 dpm/mg Hb and 151, 272, 626 dpm/mg Hb, respectively). Increases in radioactivities of a minor unidentified hemoglobin adduct fraction were also observed. The ratios of specific radioactivities of β- to α-chain (8.8 ± 1.2 SEM) did not vary with the concentrations of acetaldehyde. Although the amounts of undissociated hemoglobin following reaction with HMB did not increase with increasing concentrations of acetaldehyde, the significant increase of specific radioactivities of this fraction (152, 1967, and 6562 dpm/mg Hb for 0.1,0.2, and 0.5 mM acetaldehyde, respectively) suggested possible crosslinks within the tetramer or dimer. The amino acid analysis of α- and β-subunit adducts formed with 0.1 and 0.5 mM acetaldehyde showed that unreacted cysteine residues were more often detected at the higher acetaldehyde concentration consistent with the formation of cysteine adducts labile to acid hydrolysis or the shielding of cysteine residues in acetaldehyde-modified Hb against the subunit separation by HMB treatment. Thus acetaldehyde reacts differentially with the α- and β-hemoglobin subunits and with the undissociated hemoglobin molecule.