ENDOGENOUS NITRIC OXIDE PRODUCTION AFTER EXERCISE 416

Abstract

Intestinal mucosal damage, increased permeability and gastrointestinal (GI) complaints have been found after endurance exercise. This may result in immune responses and endogenous nitric oxide (NO) production. The aim of the study was to examine the effect of a ½ triathlon on NO production measured by urinary nitrite in 18 well-trained male triathletes (aged 34±6(±SD) yrs, ˙VO2max 67.4±9.0 ml/kg/min). Urine was collected in the morning, afternoon and evening of a resting day (23.00-7.00h, 7.00-15.00h, 15.00-2300h). On the triathlon day, urine was collected in the morning (23.00-7.00h), the first urine portion post-exercise (in the afternoon), and during the evening (till 23.00h). Urine was also collected on 4 mornings post-exercise. Urine was analyzed for nitrite and creatinine. Urinary nitrate was reduced to nitrite before analysis. Athletes were on a nitrite/nitrate restricted diet on the days of and prior to urine collection. Blood samples for endotoxin analysis were taken on the resting day and within 30 minutes after the race. Urinary nitrite and the ratio nitrite/creatinine were both higher at the evening of the triathlon day (1.06±0.20 mmol/8h; 0.21±0.02) than at the evening of the resting day(0.74±0.09 mmol/8h; 0.15±0.02) (P<0.05, paired t-test). All other urine values did not differ from resting day values. Urine values from athletes with GI complaints during or after the race (n=10) did not differ from athletes without GI complaints (n=8). Endotoxemia was not found before or after the race. In conclusion, exercise stimulates endogenous NO production, which may have been caused by immune responses and increased intestinal permeability, although the latter was not confirmed by endotoxemia.