Histochemical and chemical demonstration of reactive aldehyde groups in elastin.

Abstract

To ascertain the presence of free aldehyde radicals in elastic fibers, a histochemical method using the Sawicki reagent (N-methyl-benzothiazolone hydrazone) was employed. Three separate studies were conducted on the elastic tissue of bovine ligamentum nuchae. The elastic fibers were tested (a) in native state, (b) after extraction using an autoclave method and (c) after hot NaOH treatment. Free aldehyde radicals were detected histochemically in native and treated fibers, indicating a close attachment of the carbonyl groups to the fibrous-protein component of the elastic material. Pretreatment of the sections with NaBH4 or with NaHSO3 abolished the staining, indicating that the aldehydes in elastin can be reduced or blocked by the addition of bisulfite compounds. The presence of free carbonyl compounds in elastin was confirmed by chemical data with a new chromatographic technique. Using QAE Sephadex column pretreated with sodium bisulfite, aldehyde-bearing peptide fractions could be isolated from the elastin fibers.