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The in vitro response of sheep platelets to platelet activating factor (PAF) was investigated. Sheep platelet-rich plasma aggregated in response to PAF with an EC50 of 10 nM. Platelets isolated via arabinogalactan density gradient centrifugation displayed an EC50 of 50 pM with a threshold response at 0.1 pM. PAF-induced release of 14C-serotonin from isolated sheep platelets was comparable with an EC50 of 50 pM and threshold release at 10 fM. PAF-induced aggregation was specific in that it could be blocked by the competitive receptor antagonists Alprazolam (Upjohn, IC50 = 40 microM), L-652,731 (MSD, IC50 = 6 microM), and WEB 2086 (Boehringer Ingelheim, IC50 = 0.8 microM). At micromolar concentrations, WEB 2086 did not inhibit ADP- or thrombin-induced aggregation nor thrombin-induced serotonin release. However, at higher concentrations of WEB 2086 some inhibition of thrombin-induced platelet aggregation and release was observed. Subsequent experiments demonstrated that high concentrations of WEB 2086 can inhibit thrombin-induced clotting (Ki = 866 microM) and cleavage of the chromogenic substrate Spectrozyme-TH (Ki = 842 microM). In summary, the response of isolated sheep platelets to PAF was specifically inhibitable and was 10 to 100 times more sensitive than washed rabbit platelets, the most popular bioassay currently in use.
D G Moon, and
H van der Zee, and
K D Morton, and
J A Krasodomski, and
J E Kaplan, and
J W Fenton
January 1989,
Canadian journal of physiology and pharmacology,
D G Moon, and
H van der Zee, and
K D Morton, and
J A Krasodomski, and
J E Kaplan, and
J W Fenton
January 1994,
Life sciences,
D G Moon, and
H van der Zee, and
K D Morton, and
J A Krasodomski, and
J E Kaplan, and
J W Fenton
September 1989,
Thrombosis research,
D G Moon, and
H van der Zee, and
K D Morton, and
J A Krasodomski, and
J E Kaplan, and
J W Fenton
March 1992,
Lipids,
D G Moon, and
H van der Zee, and
K D Morton, and
J A Krasodomski, and
J E Kaplan, and
J W Fenton
January 1989,
Sheng li ke xue jin zhan [Progress in physiology],
D G Moon, and
H van der Zee, and
K D Morton, and
J A Krasodomski, and
J E Kaplan, and
J W Fenton
February 1985,
Biochemical and biophysical research communications,
D G Moon, and
H van der Zee, and
K D Morton, and
J A Krasodomski, and
J E Kaplan, and
J W Fenton
January 1997,
Biochimica et biophysica acta,
D G Moon, and
H van der Zee, and
K D Morton, and
J A Krasodomski, and
J E Kaplan, and
J W Fenton
July 1991,
Human reproduction (Oxford, England),
D G Moon, and
H van der Zee, and
K D Morton, and
J A Krasodomski, and
J E Kaplan, and
J W Fenton
August 1991,
Journal of pharmacological methods,
D G Moon, and
H van der Zee, and
K D Morton, and
J A Krasodomski, and
J E Kaplan, and
J W Fenton
October 1994,
Journal of immunological methods,
