Characterisation of species differences in the platelet ADP and thrombin response.
BACKGROUND
A number of animal models are used to study platelet-dependent diseases. In the present investigation, we have used a simple flow cytometry assay to evaluate platelet function in man, rat, mouse, guinea pig and dog.


METHODS
Platelet activation was evaluated in diluted whole blood by measuring fibrinogen binding to activated platelets using a polyclonal anti-human fibrinogen antibody that cross-reacts with fibrinogen from all species tested. The assay was used to evaluate platelet function with respect to ADP and thrombin sensitivity. The relative importance of the two platelet ADP receptors and total ADP in the thrombin response was also studied by using receptor-specific antagonists and apyrase, respectively.


RESULTS
Mouse platelets were most sensitive to both agonists. Unlike in man and dog the maximal response to ADP was greater than to thrombin in mouse, rat and guinea pig. P2Y(12) blockade was in all species equally effective as ADP removal in inhibiting thrombin-induced platelet activation whereas P2Y(1) blockade was almost ineffective.


CONCLUSIONS
The present study describes a simple platelet function test that can be used to evaluate platelet function in man, rat, mouse, guinea pig and dog. Platelets from the tested species differed in their sensitivity to ADP and thrombin. In contrast to human and canine platelets, mouse, rat and guinea pig platelets displayed a stronger maximal response to ADP than to thrombin. In terms of the relative contribution of P2Y(1) and P2Y(12) in the thrombin response, the P2Y(12) receptor was the key receptor in all species and its blockade gave equal effect as total removal of ADP.
Nylander
Sven
S
Department of Molecular Pharmacology, Preclinical R and D, AstraZeneca R and D, Mölndal, 431 83 Mölndal, Sweden. sven.nylander@astrazeneca.com
Mattsson
Christer
C
Lindahl
Tomas L
TL
D000244:Adenosine Diphosphate / Q000494:pharmacology*; D000818:Animals; D001081:Apyrase / Q000378:metabolism; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005260:Female; D005340:Fibrinogen / Q000378:metabolism; D005434:Flow Cytometry; D006168:Guinea Pigs; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D058919:Purinergic P2 Receptor Antagonists; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D012016:Reference Values; D013045:Species Specificity; D013917:Thrombin / Q000494:pharmacology*
D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D000244:Adenosine Diphosphate; D005340:Fibrinogen; D013917:Thrombin; D001081:Apyrase