Characterization of hydrogen sulphide reaction with rat‐tail tendon Type I collagen in vitro

Abstract

Type I acid‐soluble rat‐tail tendon collagen was reacted up to four days with hydrogen sulphide (H2S) concentration equivalent to that produced by putrefying saliva in in vitro systems. After reaction, the head‐space was assayed for H2S by gas chromatography (GC), and the reaction mixture was separated into salt‐soluble supernatant fraction and sediment which was solubilized in 0.5 M acetic acid. Both fractions were analyzed by SDS‐polyacrylamide gel disc electrophoresis (SDS‐PAGE) and assayed for free aldehyde, free thiol, total available thiol, and hydroxyproline content. The GC analysis of head‐space samples showed that more than 85% of the added H2S was absorbed within the initial 24 h by the reaction medium and totally removed from the head‐space in four days. Although no discernible qualitative or quantitative changes were visually detected in H2S‐treated systems by SDS‐PAGE, increased levels of hydroxyproline in the supernatant fraction indicated production of a neutral salt‐soluble product. Chemical analysis showed that the reaction resulted in the incorporation of H2S in free thiol and disulphide forms in both fractions. [35S]‐H2S/paper chromatography methods confirmed that H2S was incorporated into collagen. An increase in free aldehyde groups of both fractions inferred exposure of aldehyde groups presumably through cleavage of intramolecular cross‐linkages.The reversion of acid‐soluble collagen to a more soluble product, which is considered more susceptible to enzymatic degradation, suggests one mechanism how the volatile thiol compounds may contribute to the etiology of periodontal disease.