Effect of methyl mercaptan on synthesis and degradation of collagen

Measurements of the conversion of [14C]-proline to [14C]-hydroxyproline were employed to assess the effect of methyl mercaptan on intra- and extracellular metabolism of collagenous proteins in human gingival fibroblast cultures. Following a 30-min pulse, 10 ng of methyl mercaptan per ml of 95% air/5% CO2 head-space suppressed collagen synthesis by 39% and increased the intracellular degradation of newly synthesized collagen from 26% to 42%. Parallel cultures assayed for proline transport demonstrated a 29% inhibition of [14C]-proline uptake. A similar analysis of cultures exposed to methyl mercaptan for 12 h revealed an increase in intracellular degradation (20% control vs. 30% test) and a marked increase in extracellular collagenolysis (4% control vs. 55% test). While pulsing, collagen synthesis was decreased by 39%. Slab gel electrophoresis also demonstrated that treatment with methyl mercaptan caused reductions both in mature alpha 1 and alpha 2 chains of type I collagen and in type III procollagen. Identities of the procollagen species were confirmed by pepsin digestion. Reverse transcribed polymerase chain reaction was utilized to compare expression of alpha 1 chains of type I procollagen with type III procollagen and indicated suppression of mRNA synthesis for type III procollagen in cultures exposed to methyl mercaptan.