Negative modulation of nitric oxide production by neurotensin as a putative mechanism of the diuretic action of SR 48692 in rats

1. We investigated the effect of the non-peptide neurotensin (NT) antagonist SR 48692 on renal function in rats and the involvement of nitric oxide (NO) in the diuretic action of this compound.
2. In fed animals, SR 48692 dose-dependently (0.5 to 12.5 mg kg⁻¹, p.o., 0.03 to 1 mg kg⁻¹, i.p. and 0.1 to 1 μg/rat, i.c.v.) increased urine output and urinary excretion of Na⁺, K⁺ and Cl⁻ and reduced urine osmolality. The diuretic activity was also evident in water-deprived, fasted animals and in fasted, water-loaded rats.
3. NT (0.1 μg/rat, i.c.v.) had no effect on urine output in fed rats, but reduced the diuretic action of SR 48692 (1 μg/rat, i.c.v.). The opposite result was obtained in fasted, water-loaded animals: NT dose-dependently (0.01 and 0.1 μg/rat, i.c.v.) inhibited diuresis and this effect was significantly inhibited by i.c.v. SR 48692. In this experimental condition, SR 48692 did not further increase the on-going diuresis.
4. The NO synthesis inhibitor N^ω-nitro-L-arginine methyl ester (L-NAME; 30 mg kg⁻¹, i.p.) alone had no effect on urine output in fed rats but prevented the diuretic action of i.c.v. or i.p. SR 48692; L-arginine (1 g kg⁻¹, i.p.) but not D-arginine (1 g kg⁻¹, i.p.) restored the SR 48692-dependent increase in diuresis. L-NAME had no effect on furosemide-stimulated diuresis.
5. Systemically administered L-NAME or i.c.v. NT in fasted, water-loaded rats significantly reduced water diuresis but this effect was no longer seen in animals given i.p. L-arginine. Rats receiving i.c.v. NT, whose diuresis was significantly reduced, also excreted less nitrates and nitrites in urine.
6. Increased diuresis after central or systemic administration of SR 48692 to fed rats was paralleled by increased urinary excretion of nitrates and nitrites, this being consistent with peripheral enhancement of NO production after NT-receptor blockade by SR 48692. The increase in diuresis after furosemide also involved an increase of nitrates and nitrites in urine, but this effect was about half that attained with an equipotent diuretic dose of SR 48692.
7. In fed rats, the NO donor isosorbide-dinitrate, reduced systolic blood pressure (unlike SR 48692 which did not affect blood pressure) but also dose-dependently (1 and 5 mg kg⁻¹, i.p.) stimulated urine output.
8. The overall effects of SR 48692 strongly support a link between the actions of endogenous NT, AVP and peripheral NO production in the modulation of renal excretion of water, Na⁺, K⁺ and Cl⁻.

     

Evidence for a dilator function of 8-iso prostaglandin F2α in rat pulmonary artery

1. 8-Iso prostaglandin F_2α (8-iso PGF_2α) is one of a series of prostanoids formed independently of the cyclo-oxygenase pathway. It has been shown to be upregulated in many conditions of oxidant stress where its formation is induced by free radical-catalysed actions on arachidonic acid. As 8-iso PGF_2α is formed in vivo in diseases in which oxidant stress is high such as septic shock, we have assessed the relative potency and efficacy of this compound in pulmonary arteries from control and lipopolysaccharide (LPS)-treated rats.
2. Several studies have characterized the contractile actions of 8-iso PGF_2α on various smooth muscle preparations, but its potential dilator actions have not been addressed. Thus these studies examined both the contractile and dilator actions of 8-iso PGF_2α in rat pulmonary artery rings. The thromboxane mimetic U46619, PGE₂ sodium nitroprusside (SNP) and acetyl choline (ACh) were used for comparison. Each prostanoid had to be dissolved in ethanol to a maximum concentration of 1×10⁻² M. At high concentrations, ethanol directly contracted pulmonary vessels. We were therefore limited by the actions of the vehicle such that we were unable to add prostanoids at concentrations higher than 1×10⁻⁴ M. In some cases this meant that maximum responses were not achieved and in these cases the E_max and pD₂ values are apparent estimates.
3. The following rank order of potency was obtained from contractile studies; U46619>8-iso PGF_2α>PGE₂, each prostanoid producing concentration-dependent contractions (10⁻¹⁰3×10⁻⁴ M, 10⁻⁹10⁻⁴ M, 10⁻⁸10⁻⁴ M, respectively). As has been shown previously for other smooth muscle preparations, the thromboxane receptor (TP) antagonist ICI 192605, (1×10⁻⁶, 1×10⁻⁵ and 1×10⁻⁴ M), inhibited the contractions of 8-iso PGF_2α in a concentration-dependent fashion.
4. The nitric oxide synthase inhibitor, N^G-nitro-L-arginine methyl ester (L-NAME; 1×10⁻⁴ M), enhanced the contractile function of both 8-iso PGF_2α and PGE₂, but had no effect on that caused by U46619. Similarly, L-NAME inhibited the dilator function of all agents tested except the exogenous nitric oxide (NO) donor SNP, indicating that PGE₂ and 8-iso PGF_2α like ACh, act through the release of NO. The specificity of the effects of L-NAME were confirmed in studies with the inactive enantiomer D-NAME (1×10⁻⁴ M), which did not affect the contractile or the dilator actions of 8-iso PGF_2α. Furthermore, ICI 192605 enhanced the dilator actions of 8-iso PGF_2α, suggesting that the dilator component of 8-iso PGF_2α was achieved via activation of a non-TP receptor.
5. Isoprostanes may modulate vascular tone by a direct action on TP receptors to cause contraction and via a distinct receptor leading to the release of NO to cause dilatation.

     

Persistence of effects of nitric oxide synthase inhibitors: Comparisons on blood flow and plasma exudation in guinea pig skin

Plasma protein extravasation has been measured in guinea pig skin using

Full-size image

-albumin and blood flow using

Full-size image

enon (

Full-size image

e) clearance. The nitric oxide (NO) synthase inhibitors N^G-nitro-

Full-size image

-arginine methyl ester (

Full-size image

-NAME), N^G-monomethyl-

Full-size image

-arginine (l

Full-size image

NMMA) and N^G-nitro-

Full-size image

-arginine (

Full-size image

-NOArg) and the α-adrenoceptor agonist, phenylephrine, inhibited bradykinin induced plasma protein extravasation when co-injected with the peptide. The inhibitory effects of

Full-size image

-NAME and

Full-size image

-NOArg lasted for up to 8 and 4 h, respectively, whereas phenylephrine and

Full-size image

-NMMA had no persistent inhibitory effects. When co-injected with

Full-size image

e,

Full-size image

-NAME,

Full-size image

-NMMA,

Full-size image

-NOArg and phenylephrine, but not

Full-size image

-NAME, produced significant reductions in skin blood flow. When injected prior to

Full-size image

e,

Full-size image

-NAME and

Full-size image

-NOArg, but not phenylephrine or

Full-size image

-NMMA, significantly reduced flow. The effect of

Full-size image

-NAME on flow was not significant at 8 h. Thus, although the inhibitory effects of the NO synthase inhibitors on mediator induced plasma protein extravasation show correlations with their effects on blood flow, the persistent effect of

Full-size image

-NAME on exudation appears to extend beyond its effect on flow.     

Neurotoxicity and pharmacokinetics of ventriculolumbar perfusion of methyl 6-[3-(2-chloroethyl)-3-nitrosoureido]-6-deoxy-alpha-D-gluco-pyranoside (MCNU) in dogs

Summary Ventriculolumbar perfusion of methyl 6-[3-(2-chloroethyl)-3-nitrosoureido]-6-deoxy-alpha-D-glucopyranoside (MCNU), a water soluble nitrosourea with log P-0.71, may be efficacious in the treatment of subarachnoid dissemination of malignant glioma. We used 2 dogs to study the neurotoxicity and pharmacokinetics of MCNU. MCNU (1 mg), dissolved in 10 ml of artificial CSF, was administered via the right lateral ventricle during a period of 18 to 42 min and the CSF was drained by lumbar puncture. The perfusion was repeated once a week for 10 consecutive weeks. No neurological and systemic symptoms were noted after perfusion. Histological examination of the brain and spinal cord showed local denudation of the ependyma and local subependymal spongy degeneration and gliosis in the lateral ventricle into which MCNU was administered in one dog and local denudation of the ependyma in the other. When administration was over a period of 21 to 38 min, the MCNU concentration in the lumbar CSF peaked at 11.11 to 50.67 g/ml, in 28 to 78 min. The area under the drug concentration-time curve (AUC) was 1152 g×min/ml on average, significantly larger than that of ACNU. The elimination phase followed linear kinetics and the half-time was 41.1 min on average, significantly longer than that of ACNU. These findings suggest that ventriculolumbar perfusion of MCNU may be effective in the treatment of subarachnoid dissemination of malignant glioma notwithstanding some local histological changes.     

NMDA受体Ⅰ及白细胞介素-1在癫痫机制中的作用

应用北京医科大学培育的听源性癫痫易感大鼠Ｐ７７ＰＭＣ,以癫痫不易感大鼠Ｗｉｓｔａｒ为对照,系统研究了ＮＭＤＡ受体亚单位Ⅰ（ＮＲ１）与白细胞介素１（ＩＬ１）在癫痫发生发展中的作用及相互关系。实验在整体、脑片、神经细胞培养及分子水平进行。所得较有意义的结果如下：（１）在听源性惊厥易感大鼠Ｐ７７ＰＭＣ整个发育过程中脑内ＮＲ１ｍＲＮＡ的表达,以及成年鼠脑内ＮＭＤＡ受体活性（ＭＫ８０１结合）都高于对照组Ｗｉｓｔａｒ大鼠。惊厥后Ｐ７７ＰＭＣ脑内ＮＲ１ｍＲＮＡ的表达呈时间依赖性增加,惊厥后２４ｈ比惊厥前增加１１１％～２０２％;ＮＲ１反义寡核苷酸脑室注射（每μｌ１０μｇ）可显著减轻Ｐ７７ＰＭＣ大鼠惊厥程度,并可对谷氨酸引起的体外神经细胞的损伤有保护作用,抑制谷氨酸导致的神经毒性作用。由此证实ＮＲ１参与惊厥的发生发展,并与Ｐ７７ＰＭＣ大鼠的遗传性癫痫易感性关系密切。（２）在神经细胞培养中ＩＬ１β可明显剂量依赖性地（１～２５Ｕ·ｍｌ１）提高ＮＲ１ｍＲＮＡ的表达,白细胞介素１受体拮抗剂（ＩＬ１ｒａ）可阻断此效应;ＩＬ１β可剂量依赖性地提高ＮＲ１受体活性,因此提示ＩＬ１具有兴奋性神经调质的作用,其作     

小檗碱对体外培养大鼠大脑皮层神经元损伤的保护作用

体外培养大鼠胎鼠大脑皮层神经细胞,观察小檗碱（ｂｅｒｂｅｒｉｎｅ,Ｂｅｒ）对Ｎ－甲基－Ｄ－门冬氨酸（Ｎ－ｍｅｔｈｙｌ－Ｄ－ａｓｐａｒ－ｔａｔｅ,ＮＭＤＡ）、过氧化氢（Ｈ２Ｏ２）及撤血清培养引起的细胞损伤的保护作用。结果表明,培养的大鼠胚胎大脑皮层神经细胞在ＮＭＤＡ５００μｍｏｌ／Ｌ作用１０ｍｉｎ、或Ｈ２Ｏ２１００μｍｏｌ／Ｌ２４ｈ、或无血清培养４８ｈ后,细胞的死亡率及乳酸脱氢酶（ＬＤＨ）漏出率明显增加,抗氧化酶ＳＯＤ、谷胱甘肽过氧化酶（ＧＳＨ－Ｐｘ）活性显著降低,而脂质过氧化物丙二醛（ＭＤＡ）生成增多。Ｂｅｒ１０、３０μｍｏｌ／Ｌ能显著降低细胞死亡率、ＬＤＨ漏出率及ＭＤＡ的生成,且能明显提高抗氧化酶活性。提示：Ｂｅｒ可拮抗ＮＭＤＡ、Ｈ２Ｏ２及撤血清培养引起的神经细胞损伤,其机理可能与其减少膜脂质过氧化物生成,提高抗氧化酶活性有关     

N-nitro- -arginine methylester is protective against ethanol-induced gastric damage in cholestatic rats

In this study the effect of nitric oxide (NO) synthesis inhibition on ethanol-induced gastric damage was evaluated in bile duct-ligated, sham-operated and unoperated rats. The animals were injected intraperitoneally with saline, -arginine (200 mg/kg) or N^G-nitro- -arginine methylester ( -NAME) in doses of 5, 15 and 30 mg/kg, 30 min before ethanol administration. The animals were killed 1 h after ethanol administration and their stomachs were removed for measurement of gastric mucosal damage. The results showed that -NAME significantly enhanced the development of gastric mucosal lesions in sham-operated and unoperated rats, while in bile duct-ligated animals, -NAME decreased and -arginine enhanced the potentiation of ethanol-induced gastric mucosal damage. The plasma level of nitrite and nitrate was also measured and was significantly higher in bile duct-ligated rats than in control groups. The results suggest that inhibition of NO synthase with -NAME has different effects on ethanol-induced gastric damage in cholestatic groups and in normal rats and that these effects can be explained by overproduction of NO in bile duct-ligated animals.     

Additive effect of nitric oxide and prostaglandin-E2 synthesis inhibitors in endotoxin-induced uveitis in the rabbit

The involvement of nitric oxide (NO) and prostaglandin E₂ (PGE₂) was investigated in a model of intraocular inflammation induced by intravitreal injection of endotoxin (lipopolysaccharide, LPS, 10 ng) in rabbits. The severity of uveitis, the myeloperoxidase (MPO) activity in iris-ciliary body, and the protein concentration in aqueous humor were determined. Nitric oxide synthase (NOS) and cyclooxygenase (COX) activities were assessed respectively by nitrite and PGE₂ levels in aqueous humor. Treatment with inhibitors of NOS (N^G-nitro-L-arginine methyl ester, L-NAME, 50 mg/kg i.p.) or COX (diclofenac, 30 g, topically), alone or in combination, were compared to a salinetreated group. Diclofenac or L-NAME alone reduced or delayed the intensity of uveitis, and partially decreased the protein concentration in aqueous humor; diclofenac, but not L-NAME, partially reduced the polymorphonuclear leukocyte infiltration in the iris ciliary body as indicated by the MPO activity. Treatment with both inhibitors in combination diminished the clinical uveitis, the disruption of the blood-aqueous barrier and the MPO activity in the iris-ciliary body. We conclude that NO and PGE₂ have additive effects in endotoxin-induced uveitis in rabbits, and that the inhibition of both pathways would improve the therapeutical management of uveitis.accepted by M. J. Parnham     

Unlabeled hemoglobin adducts of 4,4′-methylenebis (2-chloroaniline) in rats and guinea pigs

The capacity of N-oxidized metabolites of 4,4-methylenebis(2-chloroaniline) (MBOCA) to form hemoglobin (Hb) adducts was determined in vitro, and the formation of Hb adducts following in vivo administration of MBOCA was assessed with or without prior induction of cytochrome P-450 enzymes with phenobarbital or -naphthoflavone. Hb adduct formation was determined by electron-capture GLC of MBOCA as the heptafluorobutyryl derivative following mild acid hydrolysis of protein-bound MBOCA. The method was confirmed by gas chromatography-mass spectrometry with selected ion monitoring. N-hydroxy- and mononitroso-MBOCA, but not MBOCA itself, formed adducts to rat and human Hb in vitro in a dose-related manner. Binding was inhibited by cysteine and glutathione but not oxidized glutathione or methionine. Intravenous administration of as little as 0.04 mol/kg N-hydroxy-MBOCA to rats resulted in measurable formation of MBOCA-Hb adducts (0.9 ng/50 mg Hb). Intraperitoneal administration of 0.5–50 mg/kg MBOCA to rats, and subcutaneous administration of 5–500 mg/kg MBOCA to rats and 4–100 mg/kg to guinea pigs resulted in dose-related formation of Hb adducts. MBOCA-Hb remained elevated in blood for greater than 10 weeks following a single subcutaneous dose in guinea pigs. Pretreatment of rats with phenobarbital induced microsomal benzphetamine N-demethylase (BND) activity and resulted in a small increase in in vitro N- andortho- hydroxylation of MBOCA, but did not increase in vivo Hb adducts. Pretreatment of rats with -naphthoflavone induced microsomal aryl hydrocarbon hydroxylase as well as ethoxyresorufin-O-deethylase, and increased in vitro N- but notortho-hydroxylation of MBOCA. -Naphthoflavone pretreatment increased the formation of MBOCA-Hb adducts when rats were dosed with MBOCA at 100 and 500 mg/kg, but not 20 mg/kg subcutaneously.     

3种预防产后出血方法的临床效果分析

目的 :寻找简单、方便、有效的预防产后出血的方法。方法 :将 30 0例无合并症产妇分成 3组 ,均于胎儿娩出后立即给药。A组 10 0例给缩宫素 2 0U ,静脉注射 ;B组 10 0例给米索前列醇 4 0 0μg ,口服 ;C组 10 0例给卡前列甲酯栓 1mg置入直肠内。比较 3组产后 2h出血量。结果 :A组的产后 2h出血量为 (2 5 1±s 71)mL ,B组和C组的产后 2h出血量分别为 (15 9± 6 7)mL和 (15 0± 73)mL ,A组明显多于B组和C组 ,差异有显著意义 (P<0 .0 1)。而B组和C组间差异无显著意义 (P >0 .0 5 )。结论 :米索前列醇、卡前列甲酯栓均能有效预防产后出血