Figure 3.
 Evaluation of type I collagen biosynthesis by metabolic labelling after mithramycin treatment. Confluent monolayer cultures of systemic sclerosis fibroblasts were labelled with [14C]proline under control conditions or under treatment with various concentrations of mithramycin, and collagen biosynthesis was determined employing a specific collagenase assay in pooled media plus cell lysate samples as described in "Materials and methods". (A) Collagen biosynthesis was decreased by 30% using mithramycin at 10 nmol/l and by 53% using mithramycin at 100 nmol/l. The results of one experiment are shown. (B) SDS gel electrophoresis of labelled proteins from the medium showed similar results with a 30% decrease in [14C]collagen after 10 nmol/l mithramycin treatment and about a 50% decrease after 100 nmol/l mithramycin administration. Two separate experiments, each in duplicate, were performed with similar results.