ADP Activities

Frojmovic MM, Kasirer-Friede A, Goldsmith HL, Brown EA. Surface seaeted von Willebrand factor mediates aggregation of ADP-activated platdets at moderate diear stress fadlitated by GPlb but not controlled by GPllb-llla. Thromb Haonost 1997 77 568-576. 

Surface-secreted vWF mediates aggregation of ADP-activated platelets at physiological (moderate) shear stress facilitation by GPIb but control by GPIIb-IIIa... 

Frojmovic MM, Wong T, Searcy GP. Platelets from bleeding Simmental cattle have a long dday in both ADP-activated expression of Gp Ilb-IIIa receptors and fibrinogat-dq>endent platdet aggregation. Thrombos Haanost 1996 76 1047-1052. 

Hensler ME, Frojmovic MM, Taylor RG, Hantgan RR, and Lewis JC. Platelet morphological changes and fibrinogen receptor localization initial responses in ADP-activated human jdatelets. Am J Pathol 1992 141 707-719. 

Figure 2. SFM images of surface activated human platelets following mica adhesion (a) and ADP-activated (10 M) ones (b).

Dotted lined arrows indicate activation of PFK by the product of ADP, activation of PVK by FDP and inhibition of GAPDH by the substrate GAP. 

Substrate inhibition of bovine liver glutamate dehydrogenase has not been studied in such detail. It is most marked when the NAD(P) concentration is also large (11), and is relieved by ADP. This appears to be the reason why ADP activates the enzyme when large glutamate and... 

Levels of the enzyme vary greatly in different mammalian tissues. Normally, liver is the richest source (54 lU/g), followed by kidney cortex (11 lU/g), with lower amounts in brain, gastric mucosa, lymph nodes, and lung (74). GDH s from various organs of the same species are similar, if not identical. Complete cross-reaction occurs between antibodies induced by bovine liver GDH and extracts of bovine spleen, brain, and heart 75) the enzymes from liver, brain, kidney, heart, and skeletal muscle are affected identically by purine nucleotides (17). One difference has been noted concerning the effect of phosphate, which stimulates ADP activation of the enzyme of porcine heart 76). 

DiPrisco (341) reported that under certain conditions reaction of GDH with l-fluoro-2,4-dinitrobenzene led to desensitization to both GTP inhibition and ADP activation by modification of three residues of tyrosine per hexamer. Attempts to confirm these results in this laboratory (343) have been unsuccessful. 

The platelet surface morphology change and platelet aggregation were investigated after adhesion events to mica and after addition of ADP at different concentration. Discoid platelets become spherical with numerous short and blunt irregular membrane projections and extend long filopodia after the ADP-activation in suspension. In contrast, platelet adhesion and spreading to mica involve the formation of two different actin-based structures, filopodia and lamellipodia, and the increase in area of platelet surface. 

PDMS Protrusions and ridges rf=39.7nm 20 pm length Platelet adhesion Static, in vitro ADP-activated platelets Double-structured surfaces most effective [98]... 

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