Inhibition of platelet aggregation by bovine endocardial apyrase.
OBJECTIVE
To study the anti-aggregatory effect of bovine endocardial endothelial cell (EEC)-associated apyrase.


METHODS
Cultured bovine EEC was used. Adenosine diphosphate (ADP) was analyzed by reversed phase HPLC, and rabbit platelet aggregation was measured turbimetrically.


RESULTS
Incubation of EEC with ADP 500 mumol.L-1 resulted in a progressive decrease in ADP concentration, which was paralleled by the decrease in platelet aggregating potential of the unmetabolized ADP. In the presence of aspirin (Asp 1 mmol.L-1)-treated EEC 1 x 10(9) cells.L-1, the aggregation of Asp (1 mmol.L-1) and methylene blue (10 mumol.L-1)-treated platelets in response to thrombin 500 U.L-1 and platelet activating factor (PAF 1 nmol.L-1) was markedly inhibited and was reversible, which was very similar to that in apyrase-treated platelets. The supernatants of EEC had no effect on platelet aggregation. EEC inhibited ADP (5 mumol.L-1)-induced platelet aggregation, but failed to inhibit adenosine 5'-O-(2-thiodiphosphate) (ADP-beta-S, an unmetabolizable structural analog of ADP, 15 mumol.L-1)-induced platelet aggregation.


CONCLUSIONS
ADP hydrolysis by EEC-associated apyrase is a major anti-thrombotic mechanism of bovine EEC.
Laboratory of Molecular Pharmacology, Hunan Medical University, Changsha 410078, China.
F X
FX
Yi
S L
SL
Huang
X
X
Guo
P
P
Sun
Z G
ZG
Guo
D000244:Adenosine Diphosphate / Q000378:metabolism; D000818:Animals; D001081:Apyrase / Q000494:pharmacology*; D002417:Cattle; D002478:Cells, Cultured; D004699:Endocardium / Q000166:cytology*; D004727:Endothelium / Q000166:cytology*; D005260:Female; D008297:Male; D010974:Platelet Aggregation / Q000187:drug effects*; D011817:Rabbits
D000244:Adenosine Diphosphate; D001081:Apyrase