title: The effect of chronic long-term intermittent hypobaric hypoxia on bone mineral density in rats: role of nitric oxide.
abstract: Intermittent hypoxia is the most common pattern of hypoxic exposure in humans. The effect of chronic long-term intermittent hypobaric hypoxia (CLTIHH) on bone metabolism is not investigated. We examined the effect of CLTIHH on bone metabolism and the role of nitric oxide (NO) in this process. The rats were divided into three groups in this study. The animals in groups I and II have been exposed to CLTIHH. The animals in group II were also treated with nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester. To obtain CLTIHH, rats were placed in a hypobaric chamber (430 mm Hg; 5 h/day, 5 days/week, 5 weeks). The group III (control) rats breathed room air in the same environment. At the begining of the experiments, bone mineral density (BMD) of the animals were measured, and blood samples were collected from the tail vein. After the 5-week CLTIHH period, the same measurements were repeated. Parathyroid hormone, calcium, phosphate, bone alkaline phosphatase (b-ALP), NO, interleukin 1 beta, interleukin 6, and tumor necrosis factor alpha levels were determined. The cytokines, NO levels, and BMD in CLTIHH-induced rats were higher compared with baseline and control values. The cytokines, b-ALP, and BMD increased while NO levels decreased in the group II compared with baseline values. BMD values of group II were lower than group I but higher than control group. Our results suggested that CLTIHH has positive effects on bone density. Intermittent hypoxia protocols may be developed for treatment and prevention of osteopenia and osteoporosis.
authors.affiliation: Department of Physiology, Cerrahpasa Faculty of Medicine, Istanbul University, Fatih, Istanbul, Turkey.
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Guner
authors.forename: Duygu D
authors.initials: DD
authors.lastname: Uzun
authors.forename: Muhittin O
authors.initials: MO
authors.lastname: Yaman
authors.forename: Habibe
authors.initials: H
authors.lastname: Genc
authors.forename: Remisa
authors.initials: R
authors.lastname: Gelisgen
authors.forename: Gulcan G
authors.initials: GG
authors.lastname: Korkmaz
authors.forename: Metin
authors.initials: M
authors.lastname: Hallac
authors.forename: Nermin
authors.initials: N
authors.lastname: Yelmen
authors.forename: Gulderen
authors.initials: G
authors.lastname: Sahin
authors.forename: Yesari
authors.initials: Y
authors.lastname: Karter
authors.forename: Gonul
authors.initials: G
authors.lastname: Simsek
mesh_terms: D000469:Alkaline Phosphatase / Q000097:blood; D000818:Animals; D015519:Bone Density; D002908:Chronic Disease; D016207:Cytokines / Q000097:blood; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000097:blood*; D010281:Parathyroid Hormone / Q000097:blood; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
chemical_list: D016207:Cytokines; D004791:Enzyme Inhibitors; D010281:Parathyroid Hormone; D009569:Nitric Oxide; D000469:Alkaline Phosphatase; D019331:NG-Nitroarginine Methyl Ester