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Garlic Elicits A Nitric Oxide‐Dependent Relaxation And Inhibits Hypoxic Pulmonary Vasoconstriction In Rats

2000; Wiley; Volume: 27; Issue: 10 Linguagem: Inglês

10.1046/j.1440-1681.2000.03333.x

1440-1681

SangAe Kim‐Park, David D. Ku,

Electron Spin Resonance Studies

SUMMARY 1. The aims of the present study were to determine the characteristics of garlic extract‐induced relaxation in rat isolated pulmonary arteries, its susceptibility to changes in oxygen tension and its protective effect against hypoxic pulmonary vasoconstriction. 2. In normoxia, garlic extract (3–500 μg/mL) produced a dose‐ and nitric oxide (NO)‐dependent relaxation. Following 60 min hypoxia, maximum garlic relaxation was reduced compared with control (mean (±SEM) –86±3 vs –69±2% of phenylephrine (PE) precontraction, respectively), but recovered after 60 min reoxygenation (–85±3% PE precontraction). 3. Acetylcholine (0.1 μmol/L)‐induced NO‐dependent relaxation was reduced from a control value of –76±1% to –46±4% during hypoxia and was further reduced to –35±2% after reoxygenation. 4. In endothelium‐intact arteries, hypoxic exposure resulted in a triphasic response: early transient contraction (+24±4%), followed by transient relaxation (–37±7%) and then sustained contraction (+62±5%). 5. Pretreatment with N G ‐nitro‐ L ‐arginine methyl ester abolished the early transient contraction, moderately attenuated the sustained contraction and had no effect on the transient relaxation. Mechanical endothelial disruption inhibited all hypoxia‐induced vascular changes. 6. Garlic pretreatment had no effect on the early transient contraction (+25±4%), but inhibited the transient relaxation (–5±3%; P < 0.05) and the sustained contraction (+26±5%; P < 0.05). 7. Garlic also significantly inhibited endothelin‐1‐induced contractions in a dose‐dependent manner. 8. These findings show that garlic extract modulates the production and function of both endothelium‐derived relaxing and constricting factors and this may contribute to its protective effect against hypoxic pulmonary vasoconstriction.