Connective tissue activation. XXII. A platelet growth factor (connective tissue-activating peptide-III) in human...

Connective tissue-activating peptides (CTAPs) stimulate human synovial cells to exhibit a higher rate of DNA synthesis, glycolysis, and glycosaminoglycan formation. These bioactive peptides have been isolated from human platelets (CTAP-III), lymphocytes, tumor cells, and neutrophilic leukocytes. Several other growth factors, such as somatomedins A and C and nonsuppressible insulin-like activity (soluble), have been shown to be dependent on the circulating levels of pituitary GH. In this study, we examined the human GH (hGH) dependence of CTAP-III. Platelets from children with reduced or absent hGH were examined for the presence of CTAP-III. The peptide was detected qualitatively by polyacrylamide gel electrophoresis and Ouchterlony double diffusion. CTAP-III antigen, measured by RIA, was found in normal amounts in platelet lysates from normal persons and GH-deficient patients. Biological activity of the peptide was suggested by the ability of platelet lysates to stimulate the formation of glycosaminoglycans and increase sulfate incorporation into glycosaminoglycans formed in cell cultures. In addition, normal and hGH-deficient platelet lysates contained potent mitogenic activity which increased thymidine incorporation into DNA. Platelets from GH-deficient patients also released CTAP-III normally on exposure to thrombin.