Effect on renin release of inhibiting renal nitric oxide synthesis in anaesthetized dogs

Nitric oxide plays an important role in the regulation of basal renal blood flow. This study was performed to examine whether selective inhibiti± of renal nitric oxide synthesis affects renin release in vivo. Accordingly, in six barbiturate-anaesthetized dogs renin release was examined before and after intrarenal infusion of the selective inhibitor of nitric oxide synthesis, N^G-nitro-l -arginine (NOARG). NOARG was infused into the renal artery to yield a renal arterial blood concentration of 0.4 μmol ml^-1. NOARG did not change systemic arterial blood pressure and glomerular filtration rate, but reduced basal renal blood flow by 26 ± 2%. Urine flow, sodium and potassium excretion were reduced after inhibition of renal nitric oxide synthesis. Basal renin release (3 ± 2 μg AI min^-1) was not altered by NOARG infusion (1 ± 1 μg AI min^-1). To stimulate renin release the renal artery was constricted to a renal perfusion pressure of 50 mmHg. At this perfusion pressure infusion of NOARG reduced renin release significantly from 48 ± 11 μg AI min^-1to 14 ± 4 μg AI min^-1. In conclusion, inhibition of renal nitric oxide synthesis reduces basal renal blood flow and reduces renin release stimulated by renal arterial constriction. These findings indicate that renal nitric oxide modulates both renal blood flow and renin release in vivo.     

The endothelial L-arginine/nitric oxide pathway and the renal circulation

Summary Endothelial cells contain an enzyme(s) which produces nitric oxide from L-arginine in response to a variety of mechanical stimuli as well as to autacoids and local and circulating hormones. Nitric oxide is a potent vasodilator and inhibitor of platelet function; it exerts its effects via activation of soluble guanylate cyclase and subsequent formation of cyclic 3–5-guanosine monophosphate. In the kidney, activation of the endothelial L-arginine pathway is associated with increases in renal blood flow, diuresis and natriuresis, while the glomerular filtration rate remains constant. The activity of the endothelial L-arginine pathway is impaired in hypertension and during chronic therapy with cyclosporine A. In addition, diabetes and atherosclerosis impair this pathway. Thus, the endothelial L-arginine pathway plays an important role in the local regulation of blood flow. Alterations in the activity of this pathway may play an important role in the pathophysiology of hypertension and renal disease.Abbreviations ADP Adenosine disphosphate - ATP Adenosine triphosphate - Cyclic GMP Cyclic guanosine monophosphate - EDRF Endothelium-derived relaxing factor - GFR Glomerular filtration rate - L-NMMA L-N^G-monomethyl arginine - NO Nitric oxide - PGI₂ Prostacyclin - SHR Spontaneously hypertensive rat Preprint of a lecture to be read at the 22nd Congress of the Gesellschaft für Nephrologie, Heidelberg, September 15–18, 1991 (Editor: Prof. Dr. E. Ritz, Heidelberg)     

The nitric oxide pathway is an important modulator of stress-induced fever in rats

Psychological stress evokes a number of physiological responses, including a rise in body temperature (T(b)), which has been suggested to be the result of an elevation in the thermoregulatory set point, i.e., a fever. This response seems to share similar mechanisms with infectious fever. A growing number of studies have provided evidence that nitric oxide (NO) has a modulatory role in infectious fever, but no report exists about the participation of NO in stress fever. Thus, the present study aimed to verify the hypothesis that NO modulates stress fever by using restraint stress as a model. To this end, we tested the effects of the non-specific NO synthase (NOS) inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) or its inactive enantiomer N(G)-nitro-D-arginine methyl ester (D-NAME) on colonic T(b) of restrained or unrestrained rats. A rapid increase in T(b) was observed when animals were submitted to restraint. Intravenous (i.v.) injection of L-NAME at a dose (10 mg/kg) that caused no change in T(b) when administered alone significantly attenuated the elevation in T(b) elicited by stress, indicating that the NO pathway may mediate stress fever. Moreover, intracerebroventricular (i.c.v.) L-NAME (250 microg/microl) caused a rise in T(b) of euthermic animals and enhanced stress fever, supporting that NO in the central nervous system (CNS) leads to a reduction in T(b) and, therefore, this is unlikely to be the site where NO may mediate stress fever. Taken together, these data indicate that the NO pathway plays an important role in modulating restraint stress-induced fever in rats.     

Endogenous nitric oxide as a probable modulator of pulmonary circulation and hypoxic pressor response in vivo

The objective of this study was to investigate the role of endogenous nitric oxide, formed from L-arginine, in the regulation of pulmonary circulation in vivo, with special reference to the hypoxic pressor response. In artificially ventilated open-chest rabbits, pulmonary vascular resistance at normoxic ventilation (F₁₀₂= 21 %) was 78C 16 cmH₂O ml^-l min 1000^-1 (mRU_L). Hypoxic ventilation (F₁₀₂= 10%) increased pulmonary vascular resistance to 117 ± 17 mRU_L. N^w-nitro-L-arginine methylester (L-NAME), an inhibitor of nitric oxide synthase, increased pulmonary vascular resistance at normoxic ventilation to 192 ± 28 mRU_L and during hypoxic ventilation to 462 ± 80 mRU_L. During N^w-nitro-l-arginine methylester infusion there was also an increase in mean arterial blood pressure as well as a decrease in cardiac output that was even more pronounced during hypoxic ventilation. L-arginine reversed the effect of N^w-nitro-l-arginine methylester on pulmonary vascular resistance at normoxic ventilation to 140 ± 26 mRU_L and at hypoxic ventilation to 239 ± 42 mRU_L. In spontaneously breathing closed-chest rabbits, N^w-nitro-L-arginine methylester evoked a marked decrease in arterial P_o2, and increases in respiration frequency and central venous pressure, while blood pH, P_CO2 and base excess remained unchanged. Taken together these findings indicate that endogenous nitric oxide, formed from L-arginine, might be a regulator of ventilation-perfusion matching at normoxic ventilation, and that nitric oxide acts as an endogenous modulator of the hypoxic pressor response.     

Role of nitric oxide in skeletal muscle: synthesis,distribution and functional importance

Over the last two decades, nitric oxide (NO) has been established as a novel mediator of biological processes, ranging from vascular control to long-term memory, from tissue inflammation to penile erection. This paper reviews recent research which shows that NO and its derivatives also are synthesized within skeletal muscle and that NO derivatives influence various aspects of muscle function. Individual muscle fibres express one or both of the constitutive NO synthase (NOS) isoforms. Type I (neuronal) NOS is localized to the sarcolemma of fast fibres; type III (endothelial) NOS is associated with mitochondria. Isolated skeletal muscle produces NO at low rates under resting conditions and at higher rates during repetitive contraction. NO appears to mediate cell–cell interactions in muscle, including vasodilation and inhibition of leucocyte adhesion. NO also acts directly on muscle fibres to alter cell function. Muscle metabolism appears to be NO-sensitive at several sites, including glucose uptake, glycolysis, mitochondrial oxygen consumption and creatine kinase activity. NO also modulates muscle contraction, inhibiting force output by altering excitation–contraction coupling. The mechanisms of NO action are likely to include direct effects on redox-sensitive regulatory proteins, interaction with endogenous reactive oxygen species, and activation of second messengers such as cyclic guanosine monophosphate (cGMP). In conclusion, research published over the past few years makes it clear that skeletal muscle produces NO and that endogenous NO modulates muscle function. Much remains to be learned, however, about the physiological importance of NO actions and about their underlying mechanisms.     

Nitric oxide regulates coronary blood flow at various coronary arterial pressures in intact porcine hearts

Nitric oxide (NO) is known to regulate basal coronary blood flow (CBF). The objective of the present study was to examine the importance of NO in CBF regulation at various coronary arterial pressures (CAPs) in vivo. Experiments were performed in 11 open-chest pentobarbitone sodium anaesthetized pigs. CAP was reduced in steps by a hydraulic occluder on the mid left anterior descending coronary artery (LAD) before and after a 5-min intracoronary infusion of the inhibitor of NO synthesis, A-nitro-L-arginine (NOARG, 30 /imo\ min“¹). CAP was recorded and NOARG infused through a catheter inserted into the LAD just distal to the occluder. CBF was measured by Doppler flowmetry on the LAD. NOARG significantly reduced CBF by 11±4, 20 ± 5, 10 ± 3, 15 ± 4, 19 ± 2, 25 ± 4 and 25 ± 5 mL min^-1 100 g^-1 (mean ± SE) at CAPs of 30 (n = 6), 40 (n = 9), 50 (n= 9), 60 (n = 9), 70 (n = 9), 80 (n = 8) and 90 (n = 6) mmHg, respectively. These decrements were not statistically different, but the percentage reductions in CBF after infusion of NOARG were significantly greatest at the lowest CAPs. The slight haemodynamic alterations induced by NOARG could not explain the reductions in CBF. Thus, the reductions in CBF after infusion of NOARG were caused by inhibition of a continuous NO release from the coronary endothelium. Coronary NO contributes significantly to CBF at all CAPs between 30 and 90 mmHg. The pronounced reduction in CBF during NO inhibition at the lower CAPs indicates an important vasodilating role of intact endothelium in a region supplied by a stenosed coronary artery.     

Myogenic vascular regulation in skeletal muscle in vivo is not dependent of endothelium-derived nitric oxide

The hypothesis, based on in vitro experiments on large conduit arteries, that endothelium-derived nitric oxide is a mediator of vascular myogenic reactivity was tested in cat gastrocnemius muscle in vivo. This was done by comparing, in the absence and presence of effective endothelium-derived nitric oxide blockade by the specific inhibitors N_G-monomethyl-l -arginine or N^G-nitro-l -arginine methyl ester, myogenic responses in defined consecutive vascular sections to dynamic vascular transmural pressure stimuli, to arterial occlusion (reactive hyperaemia), and to arterial pressure changes (autoregulation of blood flow and capillary pressure). The results demonstrated that the myogenic vascular reactivity to quick ramp transmural pressure stimuli was not attenuated by endothelium-derived nitric oxide blockade, but rather reinforced. The amplitude of the reactive hyperaemia response was unaffected by endothelium-derived nitric oxide blockade, but its duration was shortened because of faster myogenic constriction, especially of large-bore arterial resistance vessels > 25 μm, in the recovery phase. Both the improved myogenic responsiveness to transmural pressure stimuli and the shortening of the reactive hyperaemia by endothelium-derived nitric oxide blockade suggested that endothelium-derived nitric oxide released in vivo acts as a ‘metabolic’ factor which certainly does not improve, but rather depresses myogenic vascular reactivity. Autoregulation of blood flow and capillary pressure were well preserved in the presence of endothelium-derived nitric oxide blockade. It was concluded from the results of these multifaceted tests that myogenic vascular regulation in skeletal muscle in vivo seems independent of endothelium-derived nitric oxide. Nor did, endothelium-derived nitric oxide seem to play a role as a ‘metabolic’ mediator of the functional hyperaemia response to muscle exercise, since the magnitude of this response was the same in the absence and presence of endothelium-derived nitric oxide blockade.     

Expression of nitric oxide synthase and effect of substrate manipulation of the nitric oxide pathway in mouse ovarian follicles

BACKGROUND: Nitric oxide (NO) is a cell messenger with multiple actions in different biological systems, implicated in the control of follicle and oocyte function. NO is formed from L-arginine by isoforms of nitric oxide synthase (NOS) via NG-hydroxy-L-arginine, with L-citrulline as a byproduct. This study aimed to show how modulation of NO by manipulating NOS substrates would affect mouse follicle growth and ovulation in vitro, where vascular effects of NO are attenuated. METHODS: Immunohistochemistry [endothelial (eNOS) and inducible (iNOS)] and in situ hybridization (iNOS) were applied on mouse ovaries. Cultured follicles were also stained for iNOS by immunohistochemistry. For follicles cultured in the presence or absence of L-arginine, the ability of L-citrulline or NG-hydroxy-L-arginine to substitute for L-arginine was assessed in terms of follicle growth and ovulation. RESULTS: iNOS and eNOS were localized in oocytes and theca, with some staining in granulosa. iNOS mRNA occurred predominantly in granulosa and oocyte. Omission of L-arginine significantly reduced follicle survival and ovulation. Partial compensation for L-arginine withdrawal was achieved with L-citrulline and NG-hydroxy-L- arginine. Specific abnormalities of follicle growth were noted. CONCLUSIONS: NOS is present in mouse follicles, and its action is necessary at a local level for normal follicle development in vitro. Reduced growth, persistent basement membranes and reduced ovulation were associated with in vitro disruption of NO.     

Nitric oxide requirement for vasomotor nerve-induced vasodilation and modulation of resting blood flow in muscle microcirculation

Intravital microscopy of rabbit tenuissimus muscle was used for studies of endogenous nitric oxide as a microvascular regulator in vivo. Derivatives of were administered in order to modulate the formation of nitric oxide from L-arginine. N^w-nitro-L-arginine methylester (L-NAME) (1-100 mg kg-¹ i.v.) dose-dependently reduced microvascular diameters. A concomitant blood pressure increase and a decrease in heart rate was observed. The blood pressure increase induced by L-NAME (30 mg kg-¹) was reversed by L-arginine (1 g kg-¹) but not D-arginine. Vasodilation in response to topical acetylcholine (0.03-3 μM) was significantly inhibited by L-NAME (30 mg kg-^l), whereas vasodilation by sodium nitroprusside (300 nM) was not affected. Vasomotor nerveinduced vasodilatation, induced by stimulation of the tenuissimus nerve after neuromuscular blockade by pancuronium in animals pretreated with guanethidine, was significantly attenuated by L-NAME, an effect also reversed by L-arginine. The vasodilatation in response to active contractions of the muscle induced by motor nerve stimulation as well as the vasodilator response elicited by graded perfusion pressure reductions were unaffected by L-NAME or N^G-monomethyl-L-arginine (L-NMMA, 10-⁴ M) administered topically. Our results indicate that endogenous nitric oxide formed from L-arginine is a modulator of microvascular tone in vivo. Furthermore, the results suggest that endogenous nitric oxide is required for vasomotor nerve-induced vasodilatation, whereas it does not appear to play a role in myogenic vasodilatation or functional hyperaemia in this tissue.     

Pregnancy: Differential regulation of nitric oxide in the rat uterus and cervix during pregnancy and labour

The aim of this study was to determine if nitric oxide (NO)production and nitric oxide synthase (NOS) isoforms change withinthe uterus and cervix during pregnancy and labour either atterm or preterm. NO production was compared in the rat uterusand cervix of non-pregnant and pregnant rats on days 18–22prior to labour, day 22 during delivery, 1 day post-partum andafter treatment with either 10 mg onapristone or progesterone.Uterine NO synthesis, reflected in nitrite production, increasedduring gestation (194.2±22.6 nmol/g on day 19) comparedwith the non-pregnant state (76.2±18.4 nmollg, P <0.05)and decreased during term labour and post-partum. Furthermore,injection of lipopolysaccharide (LPS) (100 µg/rat i.p.)on day 20 of gestation resulted in a significant increase inNO synthesis after 6 h. Conversely, cervical NO synthesis andnitrite production was low in the non- pregnant (65.1±9.2nmol/g) and pregnant animals on days 18–22 of gestation(53.2±9.0 nmol/g on day 22, P >0.05), but markedlyincreased during term labour (139±28.6 nmollg, P <0.05).Treatment with the antiprogestin onapristone suppressed uterineNO production and increased cervical production while continuousadministration of progesterone from day 19 had the oppositeeffect. LPS produced a significant increase in cervical NO production in both the pregnant (8-fold) and non-pregnant (4-fold)states. All three known NOS isofonus (i.e. iNOS, nNOS and eNOS)were detected in the cervical samples but only two were presentin the uterus (iNOS and eNOS). An increase in the presence ofiNOS occurred during labour at term compared with cervices collectedfrom day 19. This was contrary to the measurements of the isoformin the uterus. Also, there was a similar increase of nNOS inthe cervix during labour. This isoform seemed absent in theuterus during gestation. No significant changes occurred inthe abundance of eNOS in the cervix during labour at term comparedwith day 19. During preterm labour after onapristone, 1NOS concentrationsincreased significantly in the cervix. In order to examine whetherthe NO pathway plays a role in cervical ripening, the effectsof the nitric oxide synthesis inhibitor L-nitro-arginine methylester(L-NAME) on the duration of delivery and on cervical extensibilitywere also investigated. The duration of delivery was significantlyprolonged in L-NAME.treated rats compared with the control group(2.4-fold). Moreover, cervical extens ibifity decreased significantly(1.7-fold) after in-vitro incubation with L-NAME (P <0.005).We conclude that the NO system may have an active role in thecascade of processes involved in preparing the uterus and cervixfor parturitlon.     

Pre-eclampsia-like conditions produced by nitric oxide inhibition: effects of L-arginine, D-arginine and steroid hormones

The aim of this study was to establish that inhibiting nitricoxide (NO) production with N^G-nitro-L-arginine methyl ester(L-NAME) results in high blood pressure conditions in chronicallytreated pregnant rats. To validate the model,the effects ofL-arginine (the substrate for NO) and Darginine (the stereoisomerof L-arginine which is not substrate for NO synthesis) werestudied on blood pressure and fetal weights. The effects ofa progesterone agonist, promegestone (R5020) and 17-oestradiolwere also explored. The NO synthase inhibitor L-NAME was chronicallyinfused s.c. into pregnant rats from day 17 of gestation, eitheralone or with the simultaneous infusion of L-arginine and injectionsof sex steroid hormones (promegestone and oestradiol), compoundsthat may act in the pathogenic pathways of pre-eclampsia. Systolicblood pressure was measured daily. Weight and mortality of pupswere recorded immediately after delivery. Blood pressure waselevated significantly in rats treated with L-NAME for only1 day following infusion; there was a consistent decline duringthe next 3 days of pregnancy followed by a dramatic and significantrise just prior to delivery and post-partum. Fetal weights werereduced significantly in the L-NAMEtreated rats. Co-treatmentof L-NAME-infused rats with L-arginine reversed both the increasein blood pressure and the decrease in fetal weights observedwith L-NAME alone. R5020, but not oestradiol, also reduced bloodpressure and increased fetal weights in the L-NAME-treated animals.NO appears to play essential roles in the regulation of bloodpressure during pregnancy, as well as in fetal perfusion andfetal weights at delivery. This study also indicates that progesterone,and not oestrogen, may regulate the vascular adaptations duringnormal pregnancy. LArginine and progesterone agonists like promegestonemay have beneficial effects on the high blood pressure levelsand reduced fetal weights associated with pre-eclampsia.     

Regulation of vascular adaptation during pregnancy and post-partum: effects of nitric oxide inhibition and steroid hormones

Treatment of pregnant rats with the nitric oxide synthase inhibitorNG-nitro-L-arginine methyl ester (L-NAME), has been shown toproduce symptoms similar to pre-eclampsia (i.e. elevated bloodpressure, proteinuria and fetal growth retardation). After L-NAMEinfusion is initiated on day 17 or 18 of gestation, the bloodpressure proceeds in a biphasic pattern (immediate rise, followedby a decline, then increasing again in the post-partum period).The blood pressure actually begins to rise prior to deliveryon days 21–22, i.e. after progesterone withdrawal occurs,suggesting that these responses may be regulated by changesin steroid hormone concentrations during pregnancy. Therefore,we evaluated the effects of the different steroid hormones:progestins (progesterone, promegestone, levonorgestrel), antiprogestins(mifepristone), 17-oestra-diol or androgens (testosterone, dihydrotestosterone)on systolic blood pressure in pregnant, non-pregnant femaleand normal male rats with and without L-NAME treatment and spontaneouslyhypertensive male rats. The animals received continuous infusionsof L-NAME (150 mg/kg/day) or vehicle through osmotic mini-pumpsand daily s.c. injections of steroid hormones. In pregnant ratsthe pump was inserted on day 17 or 18 of gestation and steroidhormone injections were started on the first day following deliveryat term and continued daily until post-partum day 10. In non-pregnantfemale or male rats steroid hormone injections were initiated5 days after the L-NAME pump was inserted. Systolic blood pressurewas measured daily from the tail with a pneumatic tail-cuffdevice. R5020 (1.5 mg/kg/day) significantly attenuated the bloodpressure elevation induced by L-NAME during the post-partumperiod. Similarly, it lowered blood pressure in L-NAME treatednon-pregnant female rats or male rats. R5020 also lowered bloodpressure in spontaneously hypertensive male rats. Progesterone(6 mg/kg/day) had similar effects on blood pressure in the post-partumperiod, although it also lowered the blood pressure in controlanimals. Interestingly, administration of two different dosesof Ievonorgestrel (03 and 1.5 mg/kg/day) did not decrease theblood pressure in either L-NAME-infused rats or controls. Mifepristone(RU486, 30 mg/kg/day) further increased blood pressure in L-NAME-treatedrats post-partum. 17-oestradiol (30 ng/kg/day) had no effecton blood pressure in either L-NAME infused rats in the post-partumperiod or controls, whereas both testosterone (03 mg/kg/day)and dihydrotestosterone (0.3 mg/kg/day) significantly attenuatedthe blood pressure increase after L-NAME, while raising theblood pressure in vehicle-infused animals. These results suggestthat the control of systemic blood pressure during pregnancymay be modulated by steroid hormones. Progesterone may be thesteroid hormone with the major action on vascular tension duringpregnancy.     

NO对心肌细胞线粒体功能影响的病理生理学意义

目前认为,NO对心血管系统的影响远不仅是扩张血管.在心肌细胞,NO在收缩、氧耗、底物利用、凋亡和肥大的调控中都有举足轻重的影响[1,2].而线粒体(mitochondria, Mt)在上述现象中具有中心作用,因此,NO对Mt可能具有重要的调节作用.本文就近年NO对心肌Mt功能影响的研究进展综述如下.     

A role for interleukin-6 in spreading endothelial cell activation after phagocytosis of necrotic trophoblastic material: implications for the pathogenesis of pre-eclampsia

Pre-eclampsia is characterized by systemic maternal endothelial dysfunction that precedes the onset of clinical symptoms. The cause of the dysfunction is not clear but the number and the nature of trophoblasts shed from the placenta may be altered in pre-eclamptic pregnancies. These dead trophoblasts become trapped in the pulmonary capillaries and may then be phagocytosed by endothelial cells. Phagocytosis of necrotic, but not apoptotic, trophoblasts results in endothelial cell activation. We have explored the hypothesis that activation can subsequently spread to other endothelial cells via soluble factors without the need for direct contact with shed trophoblasts. Conditioned medium from endothelial cells that had phagocytosed necrotic, but not apoptotic, trophoblasts was shown to activate fresh endothelial cells due, in large part, to IL-6 secreted into the conditioned medium. The amount of IL-6 secreted in response to phagocytosis of necrotic trophoblasts was similar to the levels of IL-6 found by others in the blood of pre-eclamptic women and was substantially more than the level of IL-6 which has been reported to induce symptoms of pre-eclampsia in pregnant rats. We demonstrated that phagocytosis of both a trophoblast cell line as well as trophoblasts shed from human placentae, had this effect on two different types of endothelial cells. The role of IL-6 in endothelial cell activation was confirmed using recombinant IL-6 and neutralizing antibodies against IL-6 and the IL-6 receptor. Thus, IL-6 secreted by pulmonary endothelial cells after they have phagocytosed necrotic trophoblasts that are trapped in the pulmonary capillaries could activate endothelial cells in other remote vascular beds, contributing to the systemic activation of the endothelium that is a hallmark of pre-eclampsia.     

Relative significance of the nitric oxide (NO)/cGMP pathway and K+ channel activation in endothelium‐dependent vasodilation in the femoral artery of developing piglets

Mechanisms mediating endothelium‐dependent vasodilation were investigated in femoral artery rings from <2‐day‐old (newborn) and 2‐week‐old piglets. Based on previous results we hypothesized an age difference in the relative contribution of nitric oxide(NO)‐cyclic 3′,5′‐guanosine monophosphate (cGMP) and K⁺ channel‐activation to acetylcholine (ACh)‐induced vasodilation. Changes in vascular tone were studied in organ baths in the absence or presence of NO synthase(NOS) inhibition or K⁺ channel blockade and the intra‐arterial accumulation of cGMP in response to ACh was measured with radioimmunoassay (RIA). In control experiments, relaxant responses to ACh were equal in the two age groups. In the presence of the NOS‐inhibitors N ^G‐monomethyl‐L ‐arginine acetate (L ‐NMMA; 100 μM ) or N^G‐nitro‐L ‐arginine (L ‐NOARG; 1–100 μM ), however, relaxation was significantly more reduced in femoral artery rings from 2‐week‐old than from newborn, with lower pD₂ values in the older age group. Inhibition of large (BK_Ca) conductance calcium‐sensitive K⁺ channels with tetraethylammonium chloride (TEA; 1 mM ), gave a significant rightward shift in the concentration‐response curves to ACh which was of the same magnitude in both age groups. The ACh‐induced vasodilation was abolished in both age groups by high K⁺ (20 mM ) in combination with L ‐NOARG (100 μM ). The relative increase in cGMP levels after addition of ACh (10 nM ) was significantly larger in rings from newborn compared with 2‐week‐old piglets (12‐ vs. four‐fold). In summary, sensitivity to NOS inhibition increased with age while the effect of K⁺ channel blockade with TEA was the same in femoral artery rings from newborn to 2‐week‐old piglets. Lower sensitivity to NOS inhibition and a larger increase in cGMP in response to ACh could indicate a higher efficacy of the NO/cGMP pathway in this vessel in the newborn piglet.     

The 1991 Ulf von Euler Lecture:The l-arginine: nitric oxide pathway

‘We must always guard the liberties of the mind and remember that some degree of heresy is often a sign of health in spiritual life.’ U. S. von Euler, Circulation, 26 (1962), 1233.     

内皮型一氧化氮合酶运输介导物在子痫前期患者胎盘组织中的定位及定量研究

目的探讨内皮型一氧化氮合酶运输介导物(endothelial n itric oxide synthase traffic inducer,NOSTR IN)在子痫前期(pre-ec lampsia,PE)患者胎盘血管内皮细胞中表达的变化及其在子痫前期发病过程中的作用。方法HE染色后镜下观察胎盘组织及血管的病理变化,免疫组织化学方法及W estern b lot检测子痫前期患者胎盘组织中NOSTR IN的表达。结果HE染色显示子痫前期患者胎盘绒毛血管变细,数目减少,血管合体膜增厚,纤维素样坏死明显多于正常妊娠;免疫组织化学显示正常妊娠和子痫前期患者胎盘血管内皮细胞中都有NOSTR IN的表达,但子痫前期患者胎盘血管内皮细胞胞浆染色较正常妊娠明显增强;W estern b lot显示子痫前期患者胎盘组织中NOSTR IN的表达显著高于正常妊娠(P<0.01)。结论胎盘组织中NOSTR IN表达增加可能是子痫前期发病机制的重要环节之一。     

Endothelial nitric oxide synthase gene (NOS3) variant and hypertension in pregnancy

Hypertension in pregnancy (HP), including preeclampsia, is known to be a multifactorial disease. Recently, a Glu298Asp variant of the endothelial nitric oxide synthase gene (NOS3) was identified as being associated with coronary spasm and myocardial infarction, whereas it has been reported that endothelial nitric oxide synthase plays a role in HP. We therefore performed an association study of the Glu298Asp variant with HP among 152 HP patients and 335 normal pregnant control individuals, in the context of other risk factors before pregnancy. The frequency of the variant GA+AA NOS3 genotypes was significantly higher in the patients (0.23) than in the controls (0.12) (P < 0.01). Multivariate analysis revealed that family history of hypertension, TT genotype of the angiotensinogen gene (AGT), GA+AA NOS3 genotype, and prepregnancy body mass index ≥ 24 were independent potent risk factors, after adjustment for maternal age and parity. The odds ratios of the factors were 2.7, 2.3, 2.2, and 2.1, respectively. Our results suggested that the Asp298 of NOS3 is a potent, independent risk factor for HP. © 2001 Wiley‐Liss, Inc.     

Effect of N-nitrosodimethylamine on inducible nitric oxide synthase expression and production of nitric oxide by neutrophils and mononuclear cells: the role of JNK signalling pathway

In neutrophils (PMN) and mononuclear cells (PBMC), one of the enzymes responsible for nitric oxide (NO) synthesis is inducible nitric oxide synthase (iNOS). Changes in iNOS expression result from various signalling pathways including the mitogen-activated protein kinase (MAPK) pathway activated by endogenic and exogenic factors. N-nitrosodimethylamine (NDMA) is a xenobiotic with widespread occurrence in human environment and has an effect on cells of the immune system. The aim of this study was to determine the effect of NDMA on iNOS expression and NO production by human PMN and PBMC cells in the light of superoxide anion production by PMN cells. Moreover, the role of JNK and p38 pathways in NO production with involvement of iNOS was studied. Additionally, the function of JNK pathway in generation of superoxide anion was determined. Moreover, nitrotyrosine expression was studied in PMN and PBMC cells in the presence of NDMA. This work shows that NDMA increases iNOS expression and NO production by PMN and PBMC cells. In addition, elevated expression of phospho-JNK and phospho-p38, which are markers of JNK and p38 MAPK pathways activation, were observed. Lower iNOS expression and NO production by neutrophils exposed to extended action of NDMA were observed after application of inhibitor of JNK and p38 pathways. Lower phospho-p38 expression in PMN stimulated by NDMA was found as a result of arresting JNK pathway, whereas, application of inhibitor of p38 pathway resulted in enhanced phospho-JNK expression in PMN and PBMC cells. Increased ability to release superoxide anion by NDMA-stimulated PMN cells was observed. This ability was reduced after the application of inhibitor of JNK pathway. In PMN and PBMC cells exposed to NDMA, an increased expression of nitrotyrosine, which is dependant on JNK and p38 pathways that are activated by this particular xenobiotic, was observed. Generally, increased induction of iNOS related to elevated production of NO by PMN and PBMC cells exposed to NDMA may result in dysfunction of regulation of immunity responses controlled by this molecule in various conditions. Increased expression of nitrotyrosine in PMN and PBMC cells exposed to NDMA may affect their functions in an auto- and/or a paracrine way. Mutual interactions of JNK and p38 MAPK during the induction of iNOS expression in cells exposed to NDMA indicate complex mechanism of induction of iNOS synthase.