The Platelet Release Reaction During Migraine Attacks M. Gawel, M. Burkitt and F. Clifford Rose Department of Neurology, Charing Cross Hospital, London, England. Reprint requests to: F. Clifford Rose, Dept. of Neurology, Charing Cross Hospital, London, W6 8RF, England. Accepted for Publication: June 9, 1979 SYNOPSIS An investigation is reported of serum levels of Beta Thromboglobulin (BTG), a platelet release reaction specific protein, and the stable metabolites of thromboxane B2 and prostacyclin during and between migraine attacks, and in age and sex matched controls. The level of BTG in plasma from controls was 61.3 ng/ml (± 26.15), in patients during migraine attacks 127.69 ng/ml (± 82.8) whilst between attacks the level was 69.06 ng/ml. No changes were observed in the levels of the stable metabolite of thromboxane B2 and prostacyclin. The significant rise in BTG (p = < .02) during migraine attacks indicates that the platelet release reaction occurs during the headache phase. (Headache 19:323-327, 1979) Studies in migraine sufferers have shown abnormalities in platelet behaviour. Aggregability, to both 5HT and ADP can be greater than normal in migraine patients, whether measured optically1,2 or by screen filtration methods,3 particularly in complicated migraine.3 In between migraine attacks, the proportion of circulating micro-aggregates is greater than in controls and is even greater during the prodromal period.4 During the headache phase, platelet aggregability in response to 5HT, ADP, epinephrine and thrombin is decreased, a finding that parallels 5HT release during the migraine cycle. It has been suggested that in those patients where there is a platelet abnormality, prophylactic treatment with anti-aggregating agents is justified.4 The important question is whether the platelet abnormalities are a primary, inherited defect of platelets or secondary to exogenous factors which affect platelet function. Free fatty acids (FFA) have been claimed to be central in the aetiology of migraine7 and at least one of these, arachidonic acid, is a precursor of prostaglandin endoperoxides which are converted by platelet enzyme activity into a labile substance called thromboxane A2. The action of thromboxane A2 is to lower the levels of cyclic AMP in the platelet and hence precipitate shape change and aggregation.8 The vessel wall cyclo-oxygenase converts endoperoxides into prostacyclin which is released into the circulation and taken up by platelets. In the platelets it elevates the levels of Cyclic AMP and this prevents the changes in the platelet leading to aggregation. It is also a powerful vasodilator.9 There is an equilibrium between platelets which are aggregating and those which are disaggregating. The proportion of aggregated to single platelets is thought to depend on the relative local concentrations of thromboxane and prostacyclin. These products of endoperoxide metabolism are extremely unstable, with a half life of about 30 seconds, but it is possible to measure their relatively stable end-products, thromboxane B2 and 6-0X0 prostaglandin F1a, by radio-immunoassay.9 When the level of cyclic AMP in the platelet falls, a sequence of events leading to platelet aggregation follows. Firstly, the platelet undergoes shape change, it sends out long processes and elongates. Shape change can be followed by aggregation, but (Fig. 1) if the stimulus is strong enough, the release reaction occurs. During this reaction the stored contents of the platelet's granules are released and the platelet aggregation cascade starts, whereby thromboxane, 5HT, and other active substances cause other platelets to undergo release and aggregation themselves.
Among the products of the release reaction is a protein of molecular weight 35,800 (Table 1) whose function is as yet unknown, but for which there exists a satisfactory radioimmunoassay.11 The serum level of Beta Thromboglobulin (BTG) is thought to be a measure of the number of platelets3 undergoing the release reaction.10 It is important in the context of this Table 1 Platelet Specific Release Products PF4 Chondroiton-4 SO4 BTG (ß-thromboglobulin) TSP (thrombin sensitive protein) b Lysin (rabbit antibacterial protein) Anti plasminogen activator Anti plasmin Tissue culture stimulant factor Vascular permeability enhancing factor Chemotactic factor(s)
study to emphasize that an elevated level of BTG indicates a generalised platelet activation; the assay is not sensitive enough to detect purely local events, e.g. in the intracranial circulation. As current evidence points to the thromboxane/ prostacyclin system as being the most important regulator of platelet function, and as abnormalities in platelet function have been described during migraine attacks. We were interested in studying it in migraine patients both between and during attacks. We were also interested in measuring whether platelet release reaction became generalised during a migraine attack. We describe here a study of Thromboxane B2, 6-0X0 prostaglandin F1a and BTG in migraine patients, during and between attacks, and in matched controls. MATERIALS AND METHODS The patients were all attending the Charing Cross Hospital Migraine Clinic. The diagnosis of migraine, either common or classical, was made according to the criteria defined by the Headache Research Committee of the World Federation of Neurology. None of the patients had taken aspirin or any other drug having an action on platelets. The patients studied during acute attacks had come to the Clinic from home or work, except for two who were inpatients at the time of the study. Controls were paramedical and secretarial staff from the Charing Cross Hospital. Informed consent was obtained for venepuncture from both patients and controls. There were 25 patients, 16 of whom were studied during a migraine attack, 11 between attacks and 6 both during and between attacks. In two patients the BTG was measured serially during an inpatient stay. There were 13 controls, the age range and sex ratio being similar to the migraine groups (Table 2). Samples for BTG, Thromboxane B2 and 6-0X0 PGF 1a were taken from a non-occluded antecubital vein. 2.5 ml of blood for the BTG examination were put into a tube containing theophylline and prostaglandinE1, spun, and the serum stored at -20°C. The BTG concentration was then measured using a radioimmunoassay method described by Bolton et al.11 20 ml. of blood was put into a tube containing indomethacin and, after spinning, the plasma was stored at -20°C. Estimations of thromboxane B2 and 6-0X0 PGF 1a were performed according to the method described by Salmon.12 Table 2 Patient Data Patients N 25 M:F 9:16 Age range 19-63 During an attack 13 Between attacks 16 Paired observations 6
Controls 13 4:9 18-59
RESULTS The mean level of BTG did not differ significantly between migraine patients in-between attacks and controls. The mean concentration of BTG during migraine attacks was double that in samples between attacks (p
Among the products of the release reaction is a protein of molecular weight 35,800 (Table 1) whose function is as yet unknown, but for which there exists a satisfactory radioimmunoassay.11 The serum level of Beta Thromboglobulin (BTG) is thought to be a measure of the number of platelets3 undergoing the release reaction.10 It is important in the context of this Table 1 Platelet Specific Release Products PF4 Chondroiton-4 SO4 BTG (ß-thromboglobulin) TSP (thrombin sensitive protein) b Lysin (rabbit antibacterial protein) Anti plasminogen activator Anti plasmin Tissue culture stimulant factor Vascular permeability enhancing factor Chemotactic factor(s)
study to emphasize that an elevated level of BTG indicates a generalised platelet activation; the assay is not sensitive enough to detect purely local events, e.g. in the intracranial circulation. As current evidence points to the thromboxane/ prostacyclin system as being the most important regulator of platelet function, and as abnormalities in platelet function have been described during migraine attacks. We were interested in studying it in migraine patients both between and during attacks. We were also interested in measuring whether platelet release reaction became generalised during a migraine attack. We describe here a study of Thromboxane B2, 6-0X0 prostaglandin F1a and BTG in migraine patients, during and between attacks, and in matched controls. MATERIALS AND METHODS The patients were all attending the Charing Cross Hospital Migraine Clinic. The diagnosis of migraine, either common or classical, was made according to the criteria defined by the Headache Research Committee of the World Federation of Neurology. None of the patients had taken aspirin or any other drug having an action on platelets. The patients studied during acute attacks had come to the Clinic from home or work, except for two who were inpatients at the time of the study. Controls were paramedical and secretarial staff from the Charing Cross Hospital. Informed consent was obtained for venepuncture from both patients and controls. There were 25 patients, 16 of whom were studied during a migraine attack, 11 between attacks and 6 both during and between attacks. In two patients the BTG was measured serially during an inpatient stay. There were 13 controls, the age range and sex ratio being similar to the migraine groups (Table 2). Samples for BTG, Thromboxane B2 and 6-0X0 PGF 1a were taken from a non-occluded antecubital vein. 2.5 ml of blood for the BTG examination were put into a tube containing theophylline and prostaglandinE1, spun, and the serum stored at -20°C. The BTG concentration was then measured using a radioimmunoassay method described by Bolton et al.11 20 ml. of blood was put into a tube containing indomethacin and, after spinning, the plasma was stored at -20°C. Estimations of thromboxane B2 and 6-0X0 PGF 1a were performed according to the method described by Salmon.12 Table 2 Patient Data Patients N 25 M:F 9:16 Age range 19-63 During an attack 13 Between attacks 16 Paired observations 6
Controls 13 4:9 18-59
RESULTS The mean level of BTG did not differ significantly between migraine patients in-between attacks and controls. The mean concentration of BTG during migraine attacks was double that in samples between attacks (p
