title: Enhancement of Na/K pump activity by chronic intermittent hypobaric hypoxia protected against reperfusion injury.
abstract: Chronic intermittent hypobaric hypoxia (CIHH) has been shown to attenuate intracellular Na(+) accumulation and Ca(2+) overload during ischemia and reperfusion (I/R), both of which are closely related to the outcome of myocardial damage. Na/K pump plays an essential role in maintaining the equilibrium of intracellular Na(+) and Ca(2+) during I/R. It has been shown that enhancement of Na/K pump activity by ischemic preconditioning may be involved in the cardiac protection. Therefore, we tested whether Na/K pump was involved in the cardioprotection by CIHH. We found that Na/K pump current in cardiac myocytes of guinea pigs exposed to CIHH increased 1.45-fold. The K(1) and f(1), which reflect the portion of α(1)-isoform of Na/K pump, dramatically decreased or increased, respectively, in CIHH myocytes. Western blot analysis revealed that CIHH increased the protein expression of the α(1)-isoform by 76%, whereas the protein expression of the α(2)-isoform was not changed significantly. Na/K pump current was significantly suppressed in simulated I/R, and CIHH preserved the Na/K pump current. CIHH significantly improved the recovery of cell length and contraction during reperfusion. Furthermore, inhibition of Na/K pump by ouabain attenuated the protective effect afforded by CIHH. Collectively, these data suggest that the increase of Na/K pump activity following CIHH is due to the upregulating α(1)-isoform of Na/K pump, which may be one of the mechanisms of CIHH against I/R-induced injury.
authors: Dept. of Pharmacology, Hebei Medical Univ., 361 East Zhongshan Road, Shijiazhuang 050017, Hebei Province, China.
authors: Hui-Cai
authors: HC
authors: Guo
authors: Fang
authors: F
authors: Guo
authors: Li-Nan
authors: LN
authors: Zhang
authors: Rong
authors: R
authors: Zhang
authors: Qing
authors: Q
authors: Chen
authors: Jun-Xia
authors: JX
authors: Li
authors: Jian
authors: J
authors: Yin
authors: Yong-Li
authors: YL
authors: Wang
mesh_terms: D000818:Animals; D006168:Guinea Pigs; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D023421:Models, Animal; D009200:Myocardial Contraction / Q000502:physiology; D015428:Myocardial Reperfusion Injury / Q000473:pathology / Q000503:physiopathology* / Q000517:prevention & control*; D032383:Myocytes, Cardiac / Q000473:pathology / Q000502:physiology; D010042:Ouabain / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D020033:Protein Isoforms / Q000502:physiology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000502:physiology*; D016896:Treatment Outcome
chemical_list: D020033:Protein Isoforms; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase