Stimulation of Prostacyclin Synthesis by Physical Exercise in Type I Diabetes

We examined the effect of short- and long-term exercise on prostacyclin (prostaglandin l₂ [PGI₂]) and thromboxane A₂ (TXA₂) synthesis in type I (insulindependent) diabetic patients and healthy control subjects. PGI₂ synthesis was assessed by determining the urinary excretion of 6-keto-PGF_1α and 2,3-dinor-6-keto- PGF_1α and TX synthesis by measuring TXB₂ in serum and urine. In the resting state, prostanoid excretion and concentrations were similar in diabetic and control subjects. During 40 min of ergometric cycling exercise, the urinary excretion of 6-keto-PGF_1α (a hydration product of vasodilatory PGI₂) increased 5.8-fold more in the 12 control subjects than in the 15 diabetic patients (P < .02). Serum TXB2 concentration rose similarly in diabetic patients and control subjects (P < .05). During a 75-km competitive cross-country ski race (7 h, 30 min), urinary excretion of 6-keto-PGF_1α rose 1.9-fold in 7 diabetic (P < .05) and 3.3-fold in 10 control (P < .001) subjects, whereas urinary dinor excretion, reflecting vascular PGI2 synthesis more closely, increased only in the control subjects (P < .01). Urinary TXB₂ excretion remained unchanged in both groups during long-term exercise. These data suggest that diabetic patients have normal PGI₂ and TXA₂ synthesis in the resting state but diminished PGI₂ response to both acute and prolonged exercise.