Fatty acid inhibition of somatomedin (serum sulfation factor)-stimulated protein and RNA synthesis in embryonic chicken cartilage

The effects of fatty acids and serum containing somatomedin on in vitro synthesis of collagen, chondromucoprotein, general proteins and RNA were studied in embryonic chicken cartilage. Somatomedin (5 % rat serum added) stimulated ³⁵SO^2-₄, [³H]leucine and [³H]tryptophan incorporation into chondromucoprotein-rich and collagen-rich cartilage protein fractions; and [³H]proline incorporation and [³H]hydroxyproline synthesis in the collagen-rich fraction. Somatomedin also stimulated [³H]uridine incorporation into RNA. In the non-stimulated state (no serum added) butyrate and octanoate had little or no effect on amino acid incorporation into protein or uridine incorporation into RNA. In the serum stimulated state, butyrate and octanoate inhibited amino acid incorporation into protein and uridine incorporation into RNA. Such inhibition was observed only with serum containing growth hormone-dependent sulfation factor (somatomedin). Agarose column chromatography of the chondromucoprotein-rich fraction revealed that while somatomedin stimulates synthesis of all proteins of this fraction equally, butyrate inhibits stimulated chondromucoprotein synthesis to a greater extent than certain other cartilage proteins (which are inhibited little, if at all). The data indicate that somatomedin stimulates embryonic chicken cartilage RNA, collagen, chondromucoprotein and general protein synthesis. Fatty acids have little or no effect on unstimulated cartilage macromolecular synthesis. The somatomedin stimulation of RNA, collagen and chondromucoprotein synthesis, and some, but not all of protein synthesis other than collagen or chondromucoprotein, is inhibited by fatty acids.