Hyperoxic and hyperbaric-induced cardioprotection: role of nitric oxide synthase 3 |
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Authors: | Cabigas Bernadette P Su Jidong Hutchins William Shi Yang Schaefer Richard B Recinos René F Nilakantan Vani Kindwall Eric Niezgoda Jeffrey A Baker John E |
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Affiliation: | Division of Pediatric Surgery, Medical College of Wisconsin, Milwaukee, WI 53226, USA. bgcab@yahoo.com |
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Abstract: | OBJECTIVE: The relative contributions of the fraction of inspired oxygen (FIO2) and atmospheric pressure (ATM) to cardioprotection are unknown. We determined whether the product of FIO2 x ATM (oxygen partial pressure) controls the extent of hyperoxic+hyperbaric-induced cardioprotection and involves activation of nitric oxide synthase (NOS). METHODS: Adult Sprague Dawley rats (n = 10/gp) were treated for 1 h with (1) normoxia+normobaria (21% O2 at 1 ATM), (2) hyperoxia+normobaria (100% O2 at 1 ATM), (3) normoxia+hyperbaria (21% O2 at 2 ATM) and (4) hyperoxia+hyperbaria (100% O2 at 2 ATM). RESULTS: Infarct size following 25 min ischemia and 180 min reperfusion was decreased following hyperoxia+normobaria and normoxia+hyperbaria compared with normoxia+normobaria and further decreased following hyperoxia+hyperbaria treatment. l-NAME (200 microM) reversed the cardioprotective effects of hyperoxia+hyperbaria. Nitrite plus nitrate content was increased 2.2-fold in rats treated with normoxia+hyperbaria and hyperoxia+hyperbaria. NOS3 protein increased 1.2-fold and association of hsp90 with NOS3 four-fold in hyperoxic+hyperbaric rats. CONCLUSIONS: Cardioprotection conferred by hyperoxia+hyperbaria is directly dependent on oxygen availability and mediated by NOS. |
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