Response to platelet-activating factor of platelets from patients with multiple sclerosis.
The response of Multiple Sclerosis (MS) and control platelets to different concentrations of platelet-activating factor was studied. At concentrations in the range 10(-7) to 10(-5)M, it was found that the MS platelets tended to aggregate fully at lower concentrations than was the case with control platelets. At a concentration of 10(-6)M, it was found that in 19 cases the MS platelets gave a full aggregation response whilst 4 cases showed biphasic but full aggregation, whereas at this concentration the control platelets showed full aggregation in only 2 cases, biphasic but less complete aggregation in 5 cases and reversible aggregation in 16 cases. In crossover studies, it could be shown that MS platelets resuspended in control platelet-poor plasma still showed enhanced aggregability and that the response of control platelets was unaffected by resuspension in MS platelet-poor plasma. Differences were also seen in susceptibility of platelets of MS and control subjects to inhibition by indomethacin, bromophenacyl bromide (a phospholipase inhibitor) and verapamil (a Ca2+ antagonist). It is suggested that the hyperaggregability of the MS platelets could reside in the platelets themselves, and may be associated with enhanced phospholipase activity.
D000098:Acetophenones / Q000494:pharmacology; D001792:Blood Platelets / Q000502:physiology; D002118:Calcium / Q000502:physiology; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D009103:Multiple Sclerosis / Q000097:blood*; D010972:Platelet Activating Factor / Q000502:physiology*; D010974:Platelet Aggregation / Q000187:drug effects; D014700:Verapamil / Q000494:pharmacology
D000098:Acetophenones; D010972:Platelet Activating Factor; D014700:Verapamil; C006821:4-bromophenacyl bromide; D002118:Calcium; D007213:Indomethacin