[Transforming growth factors and their role in chronic liver diseases]

The transforming growth factors are endogenous polypeptide substances having own cell receptors. Among them two main factors have been isolated--transforming growth factor alpha (TGF alpha) and beta (TGF beta). TGF alpha is secreted by activated proliferating hepatocytes and by certain neoplastic cells. It stimulates the synthesis of DNA and migration of hepatic epithelial cells. In chronic liver diseases it is produced in increased amounts and stimulates then proliferation and regeneration. TGF beta is released by non-parenchymal liver cells, thrombocytes, and neoplastic cells. It inhibits the synthesis of DNA in many cells, inhibits the synthesis of albumins and fibrinogen and regulates the production of acute phase proteins. In chronic liver diseases it increases the production of fibronectin and collagen, inhibiting at the same time their enzymatic breakdown. TGF beta participates in the development and progression of hepatic fibrosis.