Heparin physiological roles

No Heparin Heparin normally occurs as a macromolecule complexed with histamine in mast cells where its physiologic role is unknown. It is extracted for commercial use from porcine intestine or bovine lung. Heparin is a mixture of straight-chain anionic glycosaminoglycans... 

Glycosaminoglycans (heparin sulphate), Tamm-Horsfall protein (THP) (Hess et al. 1991), nephro-calcin, and uropontin are other potent inhibitors of crystallization processes (Ryall 1996). However, their physiological role, if any, is disputed. The role of THP as inhibitor must be distinguished from the so-called THP kidneys, which can be seen in the first 5 days of life in neonates (Fig. 20.15) (Avni et al. 1983 Berdon et al. 1969 Starinsky et al. 1995). 

Tissue factor pathway Inhibitor Is now recognized as a major physiological Inhibitor of TF-lnItlated coagulation (16). Its main role Is to modulate factor Vlla/TF catalytic activity by a two-step process. First, TFPI binds and inactivates factor Xa by forming a TFPI/factor Xa complex. Then, the inactivated factor Xa/TFPI complex binds factor Vila within the TF/Vlla complex to modulate its catalytic activity. Additionally, TFPI potentiates the effect of heparins (i.e., TFPI is released from the vascular endothelium after injection of either unfractionated heparin or low-molecular-weight heparins [LMWHs]), which may then provide high concentrations of TFPI at sites of tissue damage... 

Physiological, Pathophysiological and Therapeutic Roles of Heparin and Heparan Sulfate... 

In this chapter, we review the physiological, pathophysiological, and therapeutic roles of heparin and heparan sulfate in different biological processes. 

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