THE LIVER AS A SOURCE OF SOMATOMEDIN

Abstract

Somatomedin [Sm, growth hormone dependent factors] activity (measured by [35S]uptake in chick embryo cartilage) was determined in serum samples simultaneously drawn from the hepatic vein, portal vein, femoral artery and femoral vein of 17 anesthetized normal adult dogs). A pool of human serum was taken as reference (Sm = 1 U[unit]/ml). Sm levels in the peripheral vein of dogs were 0.38 .+-. 0.03 U/ml mean .+-. standard error of the mean). Sm activity was greater in the hepatic vein (0.48 U/ml) than in the other vessels (0.36, 0.39, 0.38 U/ml), and the paired differences were significant (P < 0.02 to P < 0.05). In 3 dogs which received bovine growth hormone (20 IU/day), the Sm levels were significantly increased after 9 days in the femoral vein (P < 0.05) and in the hepatic vein (P < 0.05). The validity of the assay is discussed; a possible interference of non-esterified fatty acids in the assay is eliminated. The difference of Sm levels between hepatic and portal veins, related to hepatic flow measured in 7 of these dogs, indicate an important production of Sm by the liver.