Effects Of MnPO Injection Of AngⅡ On Renal Neuronal Nitric Oxide Synthase And The Of Na~+, K~+-ATPase Activity In Rats

Objective: The present study is designed to explore the effects of activation ofAT1receptor in median preoptic nucleus(MnPO)on diuretic and natriureticresponses,and to undersdand the relationships between both the Na+,K+-ATPase activityand the neuronal nitric oxide synthase(nNOS) activity in renalcortex.Methods: Experiments were performed on anesthetized SD rats. All animals underanesthesia were operated by vesicostomy,for collecting urine, for quantitation of urine andfor determination of sodium excretion. A stainless steel tube was plantedaccurately in MnPO on brain stereotaxic apparatus for microinjection. MnPOswere administrated in vivo respectively with angiotensinⅡ(AngⅡ20ng),orlosartan(5μg)and Ang Ⅱ (20ng)successively,or artificial cerebrospinalfluid(aCSF,250nl).The brain and the kidney were enucleate at different timeafter MnPO administration15min、45min、60min、75min、105min and145min. Theremoval rat brains were determined the injection siteand the renal cortex tissues wereassessed for the Na+,K+-ATPase activity and the nNOS activity.Results:1.The urine volume (ml/min)and the renal sodium excretion(μmol/min)increasedsignificantly compared with aCSF group15min after MnPO administrationwith AngⅡ,60min after that the lowest least numerical value145min after that torise for control level. There was not significant difference in the levels ofurine volume and renal sodium excretion in rats between that of MnPOadministration with losartan and with aCSF.2.The Na+,K+-ATPase activityin renal cortex decreased significantly compared with aCSF group15minafter MnPO administration with AngⅡ,60min after that the lowest least numericalvalue145min after that to rise for control level.There was not significant difference in the Na+,K+-ATPase activity in renal cortex in rats between thatof MnPO administration with losartan and with aCSF.3.60min after MnPOadministration with AngⅡ, there was a negative linear correlation betweenthe renal sodium excretion and the Na+,K+-ATPase activity in renal cortex(r=-0.952,P<0.01).4. The nNOS activity in renal cortex decreased significantlycompared with aCSF group15min after MnPO administration with Ang Ⅱ,60min after that the lowest least numerical value145min after that to rise forcontrol level. There was not significant difference in the nNOS activity inrats between that of MnPO administration with losartan and with aCSF.5.60min after MnPO administration with Ang Ⅱ,there a significant positivelinear correlation between the renal sodium excretion and the nNOS activity in renalcortex(r=0.956,P<0.01).Conclusion:(1)The diuretic and natriurretic responses is induced by MnPOadministration with Ang Ⅱ.(2)The diuretic and natriurretic responses is induced byMnPO administration with Ang Ⅱ via AT1receptors.(3)In the diuretic andnatriurretic responses induced by activation of AT1receptors in MnPO,as a element, renalNa+,K+-ATPase activity decrease take part in the procedure of the integration regulationIt take part in the procedure.(4)It is one of factors inducing the diuretic and natriurreticresponses that nNOS activity in renal cortex raise via activation of AT1receptors inMnPO.