Differences in proteins secreted by human fibroblasts and muscle cells in culture

Cell cultures of human skin fibroblasts, myoblasts, and fused muscle cells were grown in the presence of ¹⁴C]leucine or a mixture of ¹⁴C]amino acids. The proteins synthesised and secreted or leaked into the culture medium during radio-labelling were separated by one and two-dimensional PAGE and detected by fluorography. Four major bands of M_r 54 kD, 52 kD, 51 kD, and 49 kD were present at greatly increased concentration in fibroblast media. These fibroblast-specific polypeptides can be readily detected in myoblast/fibroblast cocultures with fibroblast content as low as 5%.