| Objective: A large number of studies have shown that chronicintermittent hypobaric hypoxia (CIHH) significantly enhances myocardialantioxidation and promotes the recovery of cardiac function from ischemia/reperfusion. In addition, Chronic intermittent hypobaric hypoxia (CIHH) hasmany benefits on the body function including improving glucose and lipidmetabolism, lowering down serum cholesterol and artery blood pressure,enhancing myocardial antioxidant, and protecting heart against theischemia/reperfusion (I/R) injury。The metabolic syndrome (MetS) is acomplex metabolic disorders and displays as hyperglycosemia, hyperlipemia,hypertension and higher insulin. Hypertension is the typical characteristics ofMetS which biggest threat to the cardiovascular system. The baroreflex alsoknown as the "buck or depressor reflex. Research has shown that impairedbaroreceptor reflex is an important factor in MS patients with high bloodpressure. Our previous study suggested that CIHH could not alter arterialblood pressure under normal condition, but can significantly reduce thedecrease in arterial blood pressure in acute hypoxia conditions. At the sametime, CIHH has obvious antihypertensive effect in renal hypertensive rats.Recently, the results of our study show the antihypertensive effect ofCIHH in fructose-induced metabolic syndrome of rats. The results suggest that,CIHH can antagonize pathological blood pressure changes, and maintain asteady state of blood pressure. Our study also show that CIHH facilitatecarotid sinus baroreflex, which may be one of the mechanisms CIHHconfrontation abnormal changes in blood pressure. Accordingly, we havereason to speculate that, CIHH antagonizes the hypertension through thefacilitating baroreflex in fructose-induced metabolic syndrome ratThe purpose of present study was to investigate the effect of CIHH on baroreflex and the underlying mechanism in fructose-induced metabolicsyndrome ratsMethods: Male Sprague-Dawley rats were randomly divided into fourgroups: Fructose-fed group (Fruc-fed), CIHH group, CIHH plus fructosefeeding group (CIHH-F) and control group. The rats in Fruc-fed group werefed with10%fructose in drinking water. The CIHH rats were exposed tosimulated high-altitude hypoxia in a hypobaric chamber mimicking5000maltitude for42days,6h per day The rats in CIHH-F group received both10%frucotse drinking and CIHH treatment. The rats in control group were givennatural water and kept in a normoxic enviroment, The general activity of theanimals was observed and blood pressure and body weight of the animal.Were measured in the fix time each day. Perfusation on isolated carotid sinusarea was used to observe the effect of CIHH on carotid sinus baroreflex. Afteranimal anesthetized,incision in the middle of the neck and endotrachealintubation were made. The animals independently.After bilateral carotid sinus aera fully exposed, superior laryngeal nerveand sternohyoideus were cut off Bilateral depressor nerve. bilateral cervicalsympathetic nerves, and right sinus nerves were isolated and desected.Occipital artery and superior thyroid artery were ligated. Common carotidartery was isolated and ligated. A plastic tube was inserted into the distal endof left common carotid artery (served as inlet tube) and A tube was insertedinto the external carotid artery (served as outlet tube). intrassinus pressure(ISP) was monitored by a Transducer(XH YP200) connect with the inflowtract. Sinus pressure and blood pressure (BP) were recorded simultaneously inthe RM-6240multi-channel physiological recording system (ChengduInstrument Factory).Results：1Effects of CIHH on carotid sinus baroreflex in metabolic syndromerats. Compared with control rats,carotid sinus baroreflex functionalcurve(CSB) shifted rightward in Fruc-fed rat.(peak slope,(PS),(reflexdecrease,(RD) decreaed, significantly (P <0.01);(threshold pressure,(TP) equilibrium pressure (EP) and, saturation pressure (SP) increased significantly(P <0.01), which suggests that the baroreflex was inhibited significantly.Compared with the control rats, CSB function curve shifted leftward in CIHHrats significantly. PS, RD was increased significantly (P <0.01); TP, EP, andSP decreased significantly (P <0.05-0.01). which suggestes that the baroreflexwas significantly. compared with Fruc-fed rats, CSB functional curve shiftedleftward in CIHH-F rats, PS and, RD increased significantly (P <0.01), TP, EPand SP decreased significantly (P <0.05-0.01),which suggests. that CIHHimprove carotid sinus baroreceptor reflex injury in Fruc-fed rats2Effects of glibenclamide on improvement of CSB by CIHH:Perfusation with K-H solution containing glibenclamiclamide (Gli,10umol/L)has no effect on CSB in control and (Fruc-fed)rats,but shifted CSB Tfunctional curves rightward in CIHH rats, PS and RD decreasedsignificantly(P <0.01); TP, EP and SP increased significantly (P <0.01). inCIHH-F rats,CSB function curve was shifted rightward, PS and RDdecreased significantly (P <0.01); TP and EP increased significantly (P <0.05).The results demonstrate that improvement of CSB by CIHH in metabolicsyndrome rats can be blocked partially by Gli.3Effects of L-NAME (100μmol/L) on improvement of CSB byCIHH:Perfusation with K-H solution containing L-NAME (100μ M) has noeffect on CSB in all rats, which indicates NO is not involved in improvementof CSB by CIHH.Conclusion: CSB in fructose-induced metabolic syndrome rats wasinhibited significantly; CIHH improves the inhibition of carotid sinusbaroreflex in fructose-induced metabolic syndrome rats through facilitatingcarotid sinus baroreflex, which was related with opening KATP channels;... |
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