[Effect of growth hormone on the differentiation of chondrocytes from prepuberal rabbits in serum-free culture and on the radioimmunologic activity of Sm-C/IGF1 measured in the culture medium].

This study concerns the immunoreactive somatomedin C secretion by prepubertal rabbit epiphyseal chondrocytes cultured in a defined serum-free medium. In such culture conditions, chondrocytes mainly synthesized Type II collagen (80% of total collagen) during 10 days. A small amount of Type I collagen was also found with a significant (p less than 0.05) higher level during the period of cell multiplication (6.4 +/- 1.5%) than when cells reached confluency (0.9 +/- 0.2%). During the 10 days of culture without serum and without hormone added, a Sm-C/IGF1 activity was measured by RIA at a mean level of 30 +/- 5 mU/ml/10 micrograms DNA. This value was significantly higher (p less than 0.001) than in the medium not incubated with the cells (1.7 +/- 0.9 mU/ml). When hGH was added to the culture medium during the period of cell division, the level of Sm-C/IGF1 activity was significantly elevated at 39 +/- 4 mU/ml/10 micrograms DNA (p less than 0.05) and at 55 +/- 3 mU/ml/10 micrograms DNA (p less than 0.001) with 50 ng/ml and 100 ng/ml hGH concentrations respectively. On the contrary, no difference was observed at confluency in treated and non treated cells.