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.