Effect of partially purified human somatomedin on human fetal and postnatal cartilage in vitro.

Partly purified somatomedin prepared from adult human plasma stimulated [3H]thymidine and [35S]sulphate uptake into human cartilage. At a final concentration of 0.1 U/ml somatomedin the uptake of [3H]thymidine into fetal cartilage at 18 weeks of gestation was 162 +/- 23% compared with controls. Somatomedin also increased the incorporation of [35S]sulphate into fetal cartilage to 137 +/- 22% at 18 weeks compared to controls. The same concentration of somatomedin (0.1 U/ml) also increased the incorporation of [3H]thymidine into postnatal articular cartilage to 239 +/- 69% and [35S]sulphate to 133 +/- 28% compared to controls. Human somatomedin prepared from adult plasma thus has a mitogenic effect on both fetal and postnatal cartilage. The smaller effect on fetal cartilage may reflect different forms of somatomedin and/or differences in receptors for somatomedins on adult and fetal chondrocytes.