Effect of methyl mercaptan on synthesis and degradation of collagen

Measurements of the conversion of [C-14]-proline to [C-14]-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 headspace 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 [C-14]-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.