The effect of acute and strenuous swimming on catecholamine (norepinephrine, epinephrine, dopamine) content of the tracheal smooth muscle and cardiac ventricular wall was studied in rats. In this experimnet, 10-week-old male Wistar strain rats were swum for 3 hours in 35°C warm water and the results were compared with the data of age-matched sedentary controls. There were no difference in protein content of tracheal smooth muscle and ventricular wall. There were highly significant decreases in norepinephrine content of tracheal smooth muscle and ventricular wall (tracheal smooth muscle, control rats: 305.6ng/g wet tissue, swum rats: 128. 8ng/g wet tissue, ventricular wall, control rats: 671.4±92.1ng/g wet tissue, swum rats: 316.8±77.7ng/g wet tissue).
　In contrast, a swimming for 3hr. resulted in significantly increased content of epinephrine and dopamine of tracheal smooth muscle and ventricular wall (tracheal smooth muscle, control rats: EP, 2.03ng/g wet tissue, DM, 23.6ng/g wet tissue, swum rats: EP, 4.7ng/g wet tissue, DM, 42.3ng/g wet tissue, ventricular wall, control rats: EP, 19.4±6.8ng/g wet tissue, DM, 12.4±2.9ng/g wet tissue, swum rats: EP, 28.9±6.5ng/g wet tissue, DM, 79.4±9.5ng/g wet tissue). Futhermore, we investigated the effect of isoproterenol on acetylcholine-induced tention of rat tracheal smooth muscle experimentaly. Acetylcholine-induced tention revealed a tendency of decrease in presence of isoproterenol. It is suggested that an increased dopamine content in each tissue might be a manifestation of an adaptation to the increased demands upon the each tissue in rats subjected to acute and strenuous swimming. It is concluded that prolonged swimming will be available therapy for asthma since there are possibilty which prolonged swimming by adequate condtion will increase norepineprine content in tracheal smooth muscle, and its increased content will induce relaxation of trachea.

DESCENTE SPORTS SCIENCE Vol.7/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE