LAUSR

OBJECTIVE To investigate whether salidroside (Sal) protected the rat heart from exhaustive exercise-induced injury by inducing nuclear factor erythroid 2-related factor 2 (Nrf2) expression. METHODS Forty-eight male Sprague-Dawley rats were divided into four groups (n = 12 rats per group): the control, the exhaustive swimming (ES) group, the low-dose Sal plus acute exhaustive swimming (SLE) group, and the high-dose Sal plus acute exhaustive swimming (SHE) group. In the SLE and SHE groups, 15 and 30 mg/kg Sal were administered, respectively, once a day. The rats in the control and ES groups were administered the same amount of physiological saline, respectively, once a day. On the 14th day, the rats in the ES, SLE and SHE groups underwent exhaustive swimming training once. Then cardiac function parameters and electrocardiograms were recorded. Biomarkers of myocardial injury in the serum and oxidative stress factors in the myocardial tissue were evaluated using ELISA tests. The levels of Nrf2, nuclear Nrf2 and Kelch-like ECH-associated protein 1 (Keap1) messenger RNA and proteins were assessed in the myocardium using q-PCR and Western blotting, respectively. RESULTS Compared to the control group, the ES group showed remarkable increases in serum brain natriuretic peptide (BNP), cardiac troponin I (cTnI) and reactive oxygen species levels, but significant decreases in catalase and glutathione levels (p < 0.05). Compared to the ES group, the Sal treatment decreased serum BNP and cTnI levels and alleviated the changes in levels of oxidative stress-related factors. After treatment with Sal, nuclear and intracellular levels of Nrf2 protein were increased in the myocardial cells, while the level of Keap1 protein was decreased (p < 0.05). CONCLUSIONS Sal protected the heart from exhaustive exercise induced injury, and it may improve cardiac function and cardiac bioelectricity in exhausted rats by inducing Nrf2 expression.