Connective tissue activation. XIV. Composition and actions of a human platelet autacoid mediator.
Connective tissue activating peptide-III (CTAP-III) isolated from human platelets is a potent mitogen for human connective tissue cells in culture in addition to stimulating glycosaminoglycan synthesis, glucose consumption, and lactate formation. The amino acid composition of apparently homogeneous CTAP-III was determined, confirming the presence of two disulfide links and providing a calculated molecular weight of 11,633 daltons. Comparison of the mitogenic activity of serum and plasma-serum suggests that CTAP-III is a major mitogenic component of human serum. Seventeen strains of human connective tissue cells (synovial, cartilage, dermal and thyroid) incorporated [3H]-thymidine at up to 30 times control at levels under the influence of microgram quantities of CTAP-III and caused detectable increases in thymidine incorporation at levels as low as 10-29 ng/ml. Prostaglandin E1 (0.01 microgram/ml) and dibutyryl cyclic AMP (25 microgram/ml) potentiated the glycosaminoglycan stimulating effect of CTAP-III, but not its mitogenic effect. Cycloheximide and actinomycin D blocked the biologic actions of CTAP-III. Cortisol and penicillamine had little effect on the mitogenic activity of CTAP-III, whereas antirheumatic agents such as acetylsalicylic acid and phenylbutazone opposed the mitogenic activity when added to cultures at clinically relevant concentrations. A weak antiheparin factor secreted by platelets, low affinity platelet factor 4 (LA-PF4), was shown to be similar to CTAP-III in biologic actions, electrophoretic mobility, amino acid composition, and antigenic determinants.
D000596:Amino Acids / Q000032:analysis; D001792:Blood Platelets / Q000032:analysis*; D002358:Cartilage, Articular / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D003238:Connective Tissue / Q000187:drug effects* / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis; D005947:Glucose / Q000378:metabolism*; D006025:Glycosaminoglycans / Q000096:biosynthesis*; D006801:Humans; D007773:Lactates / Q000378:metabolism*; D008934:Mitogens; D008970:Molecular Weight; D010455:Peptides / Q000032:analysis / Q000302:isolation & purification / Q000494:pharmacology; D013268:Stimulation, Chemical; D013583:Synovial Membrane / Q000187:drug effects / Q000378:metabolism
D000596:Amino Acids; D006025:Glycosaminoglycans; D007773:Lactates; D008934:Mitogens; D010455:Peptides; D004247:DNA; D005947:Glucose