Change in response with age of human articular cartilage to plasma somatomedin activity

Normal male articular cartilage (34 specimens, age range 1--30 years) has been examined in vitro for response to somatomedin (SM) activity. Basal 3H-thymidine and 35S-sulfate incorporation both decreased with increasing age of the cartilage donor. However, enhancement of isotope incorporation which was attained on addition of 10% normal plasma (containing IU SM/ml) was greatest in cartilage from adolescents in the age range 12--17 years. The mean enhancement of 3H-thymidine incorporation (expressed as % basal) was as follows: age 1--10 years = 184 +/- 28 (SE), N = 9; 12--17 years = 436 +/- 101 (11); 18--30 years = 231 +/- 49 (8); and for 35S-sulfate incorporation was 1--10 years = 389 +/- 100 (8); 12--17 years = 824 +/- 273 (11); and 18--30 years = 572 +/- 56 (8). The increased response of cartilage in the 12--17 year group suggests that a greater sensitivity to the somatomedins may contribute to the increased skeletal growth during adolesence.