In vivo and in vitro effect of liver on somatomedin generation.

The serum concentration of circulating somatomedins was measured in the blood of healthy donors and subjects with hepatic cirrhosis, and in culture media from in vitro explants of healthy and cirrhotic human liver. Serum levels of somatomedin bioactivity were significantly lower in cirrhotic subjects (0.42 +/- 0.03 U/ml; M +/- SEM) compared with age matched controls (0.99 +/- 0.03 U/ml). Radioreceptor assay of somatomedin concentrations confirmed this reduction in cirrhotic patients (0.89 +/- 0.06 U/ml) compared with controls (1.32 +/- 0.05 U/ml). A parallel reduction in somatomedin circulating binding ability was also observed (99.43 +/- 7.28% in cirrhotic and 123.5% +/- 10.8% in normal subjects). In vitro explants from normal human liver tissue produced a significant increase (0.57 +/- 0.09 U/ml) in somatomedin bioactivity contained in the medium (0.29 +/- 0.06 U/ml), while a decreased bioactivity (0.12 +/- 0.06 U/ml) was observed with explants of cirrhotic livers. These results support a role of liver in the biosynthesis of both somatomedin and somatomedin binding protein.