Endothelin-1 (ET-1) is a potent vasoconstrictor peptide, which also potentiates contractions to norepinephrine in human internal mammary and coronary vessels. Exercise causes a redistribution of blood flow, i.e., the increase in working muscles that is partly attributable to a decrease in visceral blood flow. We hypothesized that exercise causes a tissue-specific increase in ET-1 expression in internal organs. We studied whether exercise affects expression of preproET-1 mRNA in the kidneys and lungs. The rats performed treadmill running (0% grade) for 45 min at a speed of 25 m/min. The plasma concentrations of ET-1, epinephrine, and norepinephrine were greater in the exercise rats than in the sedentary control rats. The expression of preproET-1 mRNA in the kidneys was markedly higher in the exercise rats than in the sedentary control rats, whereas that in the lungs did not differ between the two groups. Therefore, the present study provides a possibility that the exercise-induced increase in production of ET-1 in the kidneys causes vasoconstriction and hence decreases blood flow in the kidneys through its direct vasoconstrictive action and/or its indirect effect of enhancing vasoconstrictions to norepinephrine.
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