Changes in the nasal NO level,nasal resistance,and nasal patency before and after exercise in normal subjects

The nasal mucosa plays an important role in human disease resistance by repeatedly constricting and expanding. The nasal membrane also shrinks after exercise and thereafter recovers gradually. We studied exercise-induced changes in nasal NO, nasal resistance, and a minimal cross-sectional area in normal subjects and discuss the role of nasal NO. Subjects were 11 healthy adults (5 men and 6 women 24-52 years of age). They underwent a 6-minute fixed-load treadmill exercise, walking about 6 km/hr for 6 minutes. The nasal NO level, nasal resistance, and minimal cross-sectional area were measured consecutively before exercise, immediately after exercise, and at 5, 10, 15, 20, 25, and 30 minutes after exercise. Nasal resistance is known to decrease immediately after exercise and thereafter gradually increases until it reaches baseline levels. The minimal cross-sectional area increases immediately after exercise, but returns to baseline levels thereafter. The nasal NO level decreases immediately after exercise, but does not show changes parallel to nasal resistance or minimal cross-sectional area. The nasal NO level increases gradually, but then suddenly decreases at around 20 or 25 minutes after exercise. Its level thus shows 2 dips. This pattern is caused by a depletion of the NO substrate. As a result, NO is required by the various exercise-induced changes in many parts of the body. These findings suggest that NO production is related to the maintenance of homeostasis.