Plasma β-thromboglobulin (βTG) level, 14C 5-hydroxytryptamine (5Ht) release, PA induced by 1-epinephrine (0.2-1.0 μM) and ADP (0.5, 1.0 and 1.5 μM), and platelet TXB2 generation and eTG release after stimulation with the 2 PA inducers, was studied in platelet rich plasma of 16 patients with myotonic dystrophy (MYD) and 14 apparently healthy controls. Plasma βTG values were higher (p< 0.011) and 5Ht release was increased (p<0.035) in the patients than controls. The extent of PA induced by

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... phrine at 1 and 3 min. or by ADP at 3 min. was significantly raised in the MYD patients. These results indicate that the platelet α2 receptor activity as well as the release reaction is increased in MYD patients. Platelet TXB2 generation and βTG release after stimulation with ADP 1.5 μM or 1-epinephrine 1 μM were significantly more pronounced in the patients than controls (p<0.01). Furtheremore, the increased TXB2 generation correlated positively with the extent of PA induced by ADP (r=0.829 and p<0.05) or 1-epinephrine (r=0.929 and p<0.01) (Spearman one tailed test). There was no such correlation in the healthy controls. These results suggest that the enhanced PA in the MYD patients is presumably mediated through the increased platelet TXB2 synthesis. The enhanced platelet function and Ca++ TXB2 synthesis in MYD patients might be due to an increase in Ca++ uptake related to a generalized membrane abnormality.Further studies of this model inclu�jng assessment of platelet α2 receptor activity and changes in Ca++ ion fluxes through the platelet membrane, may lead to a better understanding of the basic cellular abnormalities in MYD.