Demonstration of somatomedin activity of "multiplication-stimulating activity" in rabbit costal chondrocytes in culture.

Multiplication-stimulating activity (MSA), a substance obtained from conditioned medium of Buffalo rat liver cells, stimulated replication of rabbit costal chondrocytes in culture and their DNA synthesis, sulfation of glycosaminoglycans, protein synthesis, and collagen synthesis. These stimulatory effects of MSA were dose-dependent in serum-free medium, indicating that MSA has intrinsic somatomedin activity. Even after several successive passages, cultured chondrocytes were more responsive to MSA than other organ- and cell-culture systems reported. Therefore, cultured rabbit costal chondrocytes proved a good in vitro system for analysis of somatomedin actions.