Calcium in blood coagulation

The role of calcium in blood coagulation and in protein C, an anticoagulant... 

Figure 2.19 Organization of polypeptide chains into domains. Small protein molecules like the epidermal growth factor, EGF, comprise only one domain. Others, like the serine proteinase chymotrypsin, are arranged in two domains that are required to form a functional unit (see Chapter 11). Many of the proteins that are involved in blood coagulation and fibrinolysis, such as urokinase, factor IX, and plasminogen, have long polypeptide chains that comprise different combinations of domains homologous to EGF and serine proteinases and, in addition, calcium-binding domains and Kringle domains.

In addition to its role as a bone component, calcium functions as a signaling substance. Ca "" ions act as second messengers in signal transduction pathways (see p. 386), they trigger exocytosis (see p. 228) and muscle contraction (see p. 334), and they are indispensable as cofactors in blood coagulation (see p. 290). Many enzymes also require Ca "" for their activity. The intracellular and extracellular concentrations of Ca "" are strictly regulated in order to make these functions possible (see B, C, and p.388). 

In ihe mammalian body, calcium is required to insure the integrity and permeability of cell membranes. 10 regulate nerve and muscle excitubiliiy. to help maintain normal muscular contraction, and to assure cardiac rhvthmicity. Calcium plays an essential role in several of ihe enzymatic steps involved in blood coagulation and also activates certain other enzyme-catalyzed reactions not involved in any of ihe foregoing processes. Calcium is ihe niosi important element of bone sail. Together with phosphate and carbonate, calcium confers on bone most of its mechanical and structural properties. 

Ninety-nine percent of the calcinm and 85% of the phosphoms in the body are fonnd in bones, mostly a poorly crystalline hydroxyapatite Caio(P04)6(OH)2. In addition, calcium is involved in blood coagulation and is an intermediary factor between impulses and muscle contraction. Calcium has an activating effect on enzymes such as phosphorylase kinase and pyruvate dehydrogenase (lipoamide)-phosphatase. 

Calcium has many important functions. It is involved in blood coagulation, activation of muscle phosphorylase, and secretory processes. It combines with phosphate to form the hydroxyapatite of bone. 

OC contains three specific glutamyl residues at amino acid positions 17, 21, and 24, which may be converted to y-carboxyglutamyl residues by a posttranslational, vitamin K-dependent enzymatic carboxylation. This unique car-boxylated amino acid binds calcium ions and is found in various proteins involved in blood coagulation and in calcium transport, deposition, and homeostasis. Undercar-boxylated OC, which has been reported in serum in some conditions, may be related to decreased bone density and may respond to administration of vitamin K. Although OC binds calcium and hydroxyapatite, its physiological role is unknown. 

Calcium A basic element found in nearly all organized tissues. It is a member of the alkahne earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes, [nih]... 

Calcium Function in Blood Coagulation Gary L. Nelsestuen... 

A Factor in Blood Coagulation,.—Ca++ participates in the normal coagulation of shed blood. It can be replaced, partially, by the related metals. Mg. Sr and Ba. Given by mouth, calcium salts have no effect on coagulation time in normal subjects... 

The calcium ion, necessary for blood-clot formation, stimulates release of bloodclotting factors from platelets (see Blood, coagulants and anticoagulants) (25). Neuromuscular excitabihty also depends on the relative concentrations of Na", Ca ", Mg ", and (26). Upon a decrease in... 

Factors I, II, III, V, VII, VIII, IX, X, XI, XII, and XIII, Protein C, and Protein S are synthesized in the Hver. Factor III is present in many different organs throughout the body. Factor IV is the divalent cation calcium. The concentration of calcium required for normal function of the blood coagulation system is much less than required for normal physiologic function of many organs in the body, eg, myocardium. 

When the element calcium is mentioned, its function as a constituent of bone (and teeth) is likely to come to mind because most of the calcium of the body is in the bones. Calcium is, however, required for blood coagulation and is needed by muscle and other... 

Rodriguez et al. [52] determined the association free energy of DPPS in a DPPC bilayer, both in the presence and in the absence of calcium ions. They used a dual topology technique with a PC-PS hybrid, and used both thermodynamic integration and free energy perturbation to determine the free energy of DPPS association in a DPPC bilayer. They found that PS-PS association is only favorable in the presence of calcium, which has direct implications for blood coagulation. 

Mechanism of Action An electrolyte that is essential for the function and integrity of the nervous, muscular, and skeletal systems. Calcium plays an important role in normal cardiac and renal function, respiration, blood coagulation, and cell membrane and capillary permeability. It helps regulate the release and storage of neurotransmitters and hormones, and it neutralizes or reduces gastric acid (increase pH). Calcium acetate combines with dietary phosphate to form insoluble calcium phosphate. Therapeutic Effect Replaces calcium in deficiency states controls hyperphosphatemia in end-stage renal disease. 

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