Role of nitric oxide and prostaglandin in the maintenance of cortical and renal medullary blood flow

This study was undertaken in anesthetized dogs to evaluate the relative participation of prostaglandins (PGs) and nitric oxide (NO) in the maintenance of total renal blood flow (TRBF), and renal medullary blood flow (RMBF). It was hypothesized that the inhibition of NO should impair cortical and medullary circulation because of the synthesis of this compound in the endothelial cells of these two territories. In contrast, under normal conditions of perfusion pressure PG synthesis is confined to the renal medulla. Hence PG inhibition should predominantly impair the medullary circulation. The initial administration of 25 µM kg-1 min-1 NG-nitro-L-arginine methyl ester produced a significant 26 percent decrease in TRBF and a concomitant 34 percent fall in RMBF, while the subsequent inhibition of PGs with 5 mg/kg meclofenamate further reduced TRBF by 33 percent and RMBF by 89 percent. In contrast, the initial administration of meclofenamate failed to change TRBF, while decreasing RMBF by 49 percent. The subsequent blockade of NO decreased TRBF by 35 percent without further altering RMBF. These results indicate that initial PG synthesis inhibition predominantly alters the medullary circulation, whereas NO inhibition decreases both cortical and medullary flow. This latter change induced by NO renders cortical and RMBF susceptible to a further decrease by PG inhibition. However, the decrease in medullary circulation produced by NO inhibition is not further enhanced by subsequent PG inhibition.

Blunted Indomethacin-Induced Downregulation of Aquaporins by Nitric Oxide Synthesis Inhibition in Rats

The present study was aimed to determine whether nitric oxide (NO) plays a role in the regulation of aquaporin (AQP) channels in the kidney. Male Brattleboro rats (250~300 g body weight) were used. The experimental group was treated with N(G)-nitro-L-arginine methyl ester (L-NAME, 100 mg/L drinking water) for 1 week, and cotreated with indomethacin (5 mg/kg, twice a day, i.p.) for the last two days. Control groups were treated with either L-NAME for 1 week, indomethacin for 2 days, or without any drug treatment. The abundance of AQP1, AQP2 and AQP3 proteins in the kidney was determined by Western blot analysis. Indomethacin downregulated AQP channels, whereas L-NAME by itself showed no significant effects on them. The indomethacin-induced downregulation of AQP2 and AQP3 was significantly blunted in L-NAME-treated rats, while that of AQP1 was not affected. These results suggest that endogenous NO, when stimulated, may downregulate AQP channels that are specifically regulated by AVP/cAMP pathway in the kidney.

Inhibitory effect of cholecystokinin octapeptide on carotid sinus nerve afferent discharge in anesthetized rats / 中国药理学与毒理学杂志

AIM To study if cholecystokinin octapeptide (CCK-8) alter cardiovascular functions by its direct inhibitory effect on carotid sinus baroreceptor (CSB) activity. METHODS The functional curve of carotid baroreceptor (FCCB) was constructed and the functional parameters of carotid baroreceptor were measured by recording sinus nerve afferent discharge in anesthetized male rats with perfused isolated carotid sinus. RESULTS ① CCK-8 0.1, 0.5 and 1.0 μmol·L-1 shifted FCCB to the right and downward, with a marked decrease in peak slope and peak integral value of carotid sinus nerve discharge in a concentration-dependent manner, indicating the inhibitory effect of CCK-8 on CSB activity. ② Pretreatment with proglumide (100 μmol·L-1), a nonselective CCK receptor antagonist, or Bay K8644 (0.5 μmol·L-1), an agonist of calcium channel, partially attenuated the inhibitory effect of CCK-8 (0.5 μmol·L-1) on CSB activity. Pretreatment with L-NAME (100 μmol·L-1), an inhibitor of NO synthase, did not affect the inhibitory action of CCK-8. CONCLUSION CCK-8 inhibits CSB activity, which may be mediated by activating CCK receptors in the carotid sinus area and thereby resulting in an inhibition of stretch-sensitive channels and decrease in Ca2+ influx.

Effect of N~G-nitro-L-arginine on amino acid contents of ischemic brain in rat / 医学研究生学报

Objective: To investigate the beneficial effect of NG-nitro-L-arginine(L-NA) on cerebral ischemic injury and the possible mechanism by evaluating the effect of nitric oxide synthase(NOS) inhibitor,L-NA,on the contents of aspartate,glutamate,glycine and?-aminobutyric acid(GABA),respectively,in striatum,hippocampus and cortex of rat brain following cerebral ischemia. Methods:The model of focal cerebral ischemia in rat was prepared.Rats were divided into sham-operated group,ischemic group and L-NA group.Each group was further divided into 3 subgroup(n=6 for each): the middle cerebral artery occlusion(MCAO) was maintained for 2,6 and 12h,respectively.L-NA(20 mg/kg,ip) was administrated after MCAO,two times a day,for 3 consecutive days.The changes of infarcted volume and the contents of amino acids were assayed. Results:The infarcted volume(IV%) was not significantly different among the ischemic groups with or without L-NA administrated 2 or 6 h after MCAO;and was markedly decreased in the ischemic group with L-NA administrated 12 h after MCAO(P

Effect of L-NNA on GFAP production in the gerbil hippocampus after recirculation following ischemia / 中国药理学通报

AIM: To observe the effects of L-NNA on glial fibrillary acidic protein (GFAP) production in the gerbil hippocampus after recirculation following ischemia. METHODS: Both vessels occlusion and immunofluorescent methods in gerbil hippocampal tissue slices incubated in vitro were used. RESULTS: Recirculation following ischemia led to a rise on GFAP concentration in the hippocampus. GFAP positive cells mainly distributed in rediatum layer and molecullar layer in the hippocampus, L-NNA decreased GFAP synthesis. CONCLUSION: L-NNA is a strong inhibitor of nitric oxide synthase (NOS). It is possible that the role of endogenous NO mediated GFAP synthesis is inhibited by L-NNA.

Effect of L-NNA on GFAP production in the gerbil hippocampus after recirculation following ischemia / 中国药理学通报

AIM To observe the effects of L NNA on glial fibrillary acidic protein (GFAP) production in the gerbil hippocampus after recirculation following ischemia. METHODS Both vessels occlusion and immunofluorescent methods in gerbil hippocampal tissue slices incubated in vitro were used. RESULTS Recirculation following ischemia led to a rise on GFAP concentration in the hippocampus. GFAP positive cells mainly distributed in rediatum layer and molecullar layer in the hippocampus, L NNA decreased GFAP synthesis. CONCLUSION L NNA is a strong inhibitor of nitric oxide synthase(NOS). It is possible that the role of endogenous NO mediated GFAP synthesis is inhibited by L NNA.