Exercise Differentially Regulates Renalase Expression in Skeletal Muscle and Kidney

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Abstract
Renalase is a newly discovered amine oxidase and may lower blood pressure by metabolizing catecholamines. We have hypothesized that exercise and training may regulate renalase expression to control blood pressure. In this study, we investigated changes in renalase expression after exercise and training in white and red portion of the gastrocnemius muscle, kidney, and serum in rats. Rats were either untrained or subjected to six weeks of endurance training, which predominantly recruits red fibers. Rats from each group were sacrificed before (n = 10), immediately after (n = 10), or three hours (n = 10) following exercise. Renalase mRNA and protein levels were measured by RT-PCR and ELISA, respectively. There were no significant changes in renalase expression after prolonged training or acute exercise in the serum or red muscle of rats. However, in white muscle, renalase mRNA and protein levels decreased after acute exercise in untrained rats, whereas, in trained rats, its protein level remained unchanged, despite a decrease in mRNA. Thus, exercise influenced renalase expression only in white muscle fibers that are not predominantly recruited during exercise. The reduction of renalase protein in white muscle suggests that renalase may contribute to blood redistribution between contracting and non-contracting fibers during exercise. In the kidney, renalase protein levels decreased after training, while mRNA levels increased. The reduction in renalase protein levels may contribute to functional kidney hypoperfusion, which has been observed after training. In conclusion, exercise differentially regulates renalase expression in skeletal muscle and kidney.

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