Stimulation of cartilage zones of the calf costochondral growth plate in vitro by growth hormone dependent rat plasma somatomedin activity.

The actions of rat plasma somatomedin activity dependent on growth hormone were investigated in vitro on separated zones of cartilage from the calf costochondral junction. Plasma somatomedin maximally stimulated the uptake of[3H]thymidine into cartilage cells of the proliferating region. Cartilage deeper in the growth plate possessed the highest uptake of [35S]sulphate which was also stimulated by somatomedin. Somatomedin, therefore, appears to promote both cell replication and matrix synthesis throughout the growth plate cartilage although the two processes were greatest in different cartilage regions. Growth hormone or tri-iodothyronine did not directly alter the uptake of either isotope into the growth plate cartilage.