家兔十二指肠粘膜碳酸氢盐分泌机理的研究

本实验旨在探讨ＨＣＯ３－分泌的调节及其转运的离子通道。取大白兔近端十二指肠，置于尤氏小室间（ＵｓｓｉｎｇＣｈａｍｂｅｒ），测定血管活血肠肽（ＶＩＰ）、前列腺素Ｅ２（ＰＧＥ２），二丁酰环磷腺甙（ｄｂ－ｃＡＭＰ）及电刺激（ＥＦＳ）对碳酸氢盐（ＨＣＯ３－）分泌量、电流（Ｉｓｃ）和电位差（ＰＤ）的影响，以及缺氧、缺氯、缺钠和加入ＤＩＤＳ（４，４－ｄｉｉｓｏｔｈｉｏｃｙａｎｏｓｔｉｌｂｅｎｅ－２，２’－ｄｉｓｕｌｆｏｎｉｃａｃｉｄ）、哇巴因（Ｏｕａｂａｉｎ）和神经毒素（Ｔｅｔｒｏｄｏｔｏｘｉｎ，ＴＴｘ）后对上述指标的影响。结果示，ＶＩＰ、ＰＧＥ２、ｄｂ－ｃＡＭＰ和ＥＦＳ均刺激ＨＣＯ３－分泌和Ｉｓｃ、ＰＤ的升高，而缺氧、缺钠和哇巴因呈抑制作用。ＤＩＤＳ和缺氯则完全抑制由ＰＧＥ２引起的刺激作用，部分抑制（５０％）由ＶＩＰ的刺激作用，而对ｄｂ－ｃＡＭＰ则无抑制作用。ＴＴＸ抑制由ＥＦＳ引起的作用。ＨＣＯ３－分泌与ＶＩＰ、ＰＧＥ２及ｄｂ－ｃＡＭＰ引起的细胞内ｃＡＭＰ水平不成正相关。     

血管平滑肌细胞的一氧化氮活性及精氨酸加压素对其调节与高血压发病关系的研究

以培养的自发性高血压大鼠（ＳＨＲ）和正常对照大鼠（ＷＫＹ）血管平滑肌细胞（ＶＳＭＣ）为模型，动态观察了精氨酸加压素（ＡＶＰ）对动脉ＶＳＭＣ的一氧化氮合酶（ＮＯＳ）活性、一氧化氮（ＮＯ）合成的影响。结果表明：ＳＨＲ动脉ＶＳＭＣ的ＮＯＳ活性、ＮＯ含量明显低于ＷＫＹ（Ｐ＜０．０５）；ＡＶＰ对ＳＨＲ动脉ＶＳＭＣ的ＮＯＳ活性、ＮＯ合成具有显著促进效应；同一浓度ＡＶＰ作用于ＳＨＲ及ＷＫＹ动脉ＶＳＭＣ，ＷＫＹ的ＮＯＳ活性及ＮＯ含量显著高于ＳＨＲ（Ｐ＜０．０１）；ＡＶＰ作用后，动脉ＶＳＭＣ的ＮＯＳ活性与ＮＯ含量呈显著正相关。提示ＳＨＲ动脉ＶＳＭＣ的ＮＯＳ－ＮＯ系统可能功能不良；ＡＶＰ可能通过ＮＯＳ－ＮＯ途径参与高血压病的发生和发展。     

辅酶Q10拮抗精氨酸加压素对血管平滑肌细胞脂质过氧化的作用

采用体外培养的大鼠主动脉血管平滑肌细胞（ＶＳＭＣ）为模型，测定其脂质过氧化物（ＬＰＯ）含量，观察精氨酸加压素（ＡＶＰ）对ＶＳＭＣ脂质过氧化的影响和辅酶Ｑ１０（ＣｏＱ１０）的干预作用。结果显示：（１）ＡＶＰ有明显的促ＶＳＭＣ脂质过氧化作用（Ｐ＜０．０１），且时间愈长，作用愈显著。（２）ＣｏＱ１０对ＡＶＰ的促ＬＰＯ生成有明显的降低作用（Ｐ＜０．０１），并随浓度增高作用增强。此提示ＡＶＰ参与高血压发病可能与其促ＶＳＭＣ脂质过氧化作用有关；ＣｏＱ１０具有拮抗ＡＶＰ促ＶＳＭＣ脂质过氧化作用，这对高血压病的防治将有意义。     

微空间测定法在普氏立克次体物质转运研究中的应用

本文通过微空间测定法（ＭｉｃｒｏｓｐａｃｅＭｅａｓｕｒｅｍｅｎｔ）利用Ｐ３２标记的ＵＭＰ，ＵＴＰ，ＧＭＰ，ＧＴＰ，１４Ｃ—蔗糖及３Ｈ２Ｏ来测定普氏立克次体是否转运下述四种核糖核苷酸。实验结果表明，ＵＭＰ，ＵＴＰ及ＧＴＰ在立克次体内的微空间体积（Ｖｉ）分别为自由通过胞浆膜的３Ｈ２ＯＶｉ值的３．３２１，２．４６０及４．９４５倍，说明立克次体可以逆浓度差主动转运这三种核苷酸。该法测到ＧＭＰ的Ｖｉ值与用３Ｈ２Ｏ测到的Ｖｉ值之比接近１，表明ＧＭＰ在立克次体内是有空间体积的，但对ＧＭＰ转运的方式尚难肯定。本文资料证实立克次体确可从其外部生境中转运核糖核苷酸供其合成核酸之需。     

血管平滑肌细胞的一氧化氮活性及精氨酸加压素对其调节与高血 …

以培养的自发性高血压大鼠（ＳＨＲ）和正常对照大鼠（ＷＫＹ）血管平滑肌细胞（ＶＳＭＣ）为模型，动态观察了精氨酸加压素（ＡＶＰ）的对动脉ＶＳＭＣ的一氧化氮合酶（ＮＯＳ）活性，一氧化氮（ＮＯ）合成的影响。结果表明：ＳＨＲ动脉ＶＳＭＣ的ＮＯＳ活性，ＮＯ含量明显低于ＷＫＹ（Ｐ〈０．０５）；ＡＶＰ对ＳＨＲ动脉ＶＳＭＣ的ＮＯＳ活性，ＮＯ合 有显著促进效应，同一浓度ＡＶＰ作用下ＳＨＲ及ＷＫＹ动脉，ＶＳＭＣ，ＷＫＹ     

CGRP对高血压病患者动脉VSMC的NOS活性和NO合成的影响

目的:为探讨降钙素基因相关肽（ＣＧＲＰ）对高血压病（ＥＨ）患者动脉血管平滑肌细胞（ＶＳＭＣ）的一氧化氮合酶（ＮＯＳ）和一氧化氮（ＮＯ）产生的作用。方法:对ＥＨ患者和血压正常者（ＮＴ）的动脉ＶＳＭＣ进行培养,分别测定ＥＨ组和ＮＴ组ＶＳＭＣ的ＮＯ含量和ＮＯＳ活性,观察ＥＨ患者ＶＳＭＣＮＯ的产生以及ＣＧＲＰ对其的影响。结果:①基础状态下,ＥＨ组ＶＳＭＣ的ＮＯ含量和ＮＯＳ活性分别为４２．７３±６．７６μｍｏｌ／（２．５×１０６ｃｅｌｓ）和０．２４±０．０５ｎｍｏｌ／（２．５×１０６ｃｅｌｓ）,均显著低于ＮＴ组的７４．５２±４．３７μｍｏｌ／（２．５×１０６ｃｅｌｓ）和０．５５±０．１０ｎｍｏｌ／（２．５×１０６ｃｅｌｓ）（Ｐ＜０．０５）;②在ＣＧＲＰ作用下,ＥＨ组的ＮＯ含量和ＮＯＳ活性分别为８８．６３±４．１２μｍｏｌ／（２．５×１０６ｃｅｌｓ）和１０．５５±１．２８ｎｍｏｌ／（２．５×１０６ｃｅｌｓ）,均显著低于ＮＴ组的１００．４９±９．６９μｍｏｌ／（２．５×１０６ｃｅｌｓ）和１２．４５±１．６１ｎｍｏｌ／（２．５×１０６ｃｅｌｓ）（Ｐ＜０．０５）;③基础状态和ＣＧＲＰ作用下两组ＶＳＭＣ的ＮＯ含量和ＮＯＳ活性随?     

单纯疱疹病毒Ⅱ型感染极早期对离体人动脉平滑肌细胞原癌基因c-sis及c-myc表达的影响

目的：观察单纯疱疹病毒Ⅱ型（ＨＳＶ－２）感染极早期对离体人动脉平滑肌细胞（ｈＡＳＭＣ）原癌基因ｃ－ｓｉｓ及ｃ－ｍｙｃ表达的影响。方法：采用不同感染剂量的ＨＳＶ－２吸附单层ｈＡＳＭＣ１小时作为病毒感染细胞模型,应用Ｎｏｒｔｈｅｒｎ杂交方法观察上述原癌基因表达。结果：病毒吸附细胞后０分钟、３０分钟、６０分钟,病毒感染组［５感染复数（ＭＯＩ）和１０ＭＯＩ;ＭＯＩ＝空斑形成单位／细胞数（ＰＦＵ／细胞数）］均比对照组的原癌基因ｃ－ｓｉｓ、ｃ－ｍｙｃ表达增加,且基因表达与感染时间也有关。结论：ＨＳＶ－２感染可以诱导ｈＡＳＭＣ原癌基因ｃ－ｓｉｓ、ｃ－ｍｙｃ表达增加,该作用可能是病毒促进ｈＡＳＭＣ异常增殖进而参与动脉粥样硬化或血管成形术后再狭窄形成的分子机制之一。     

红细胞抗高血压因子和川芎嗪对大鼠血管平滑肌cGMP含量的影响

观察红细胞抗高血压因子（ＡＨＦ）和中药川芎嗪（ＴＭＰ）对血管平滑肌细胞环一磷酸鸟苷（ｃＧＭＰ）产生的影响。方法实验用８～１０周的Ｗｉｓｔａｒ大鼠（ｎ＝６）。分离主动脉（Ａ）及肠系膜动脉（ＭＡ），其中Ａ一半去内皮，另一半保留内皮完整，将肌条分别制备成匀浆，用放射免疫分析法测定ｃＧＭＰ含量。结果ＡＨＦ（１０－５ｇ／ｍｌ）和ＴＭＰ（１０－４ｍｏｌ／Ｌ）对血管平滑肌细胞（ＶＳＭＣ）ｃＧＭＰ生成有显著刺激作用。在ＡＨＦ作用下，Ａ组有、无内皮组和ＭＡ组ｃＧＭＰ含量分别是对照组的１．２５倍，１．２６倍和１．７２倍；在ＴＭＰ作用下的实验组ｃＧＭＰ含量分别为对照组的１．６０倍，１．５０倍和１．５２倍，与对照组比较差异均有显著性（Ｐ＜０．０５或Ｐ＜０．００１）。结论ＡＨＦ和ＴＭＰ均能升高Ａ和ＭＡｃＧＭＰ水平，且ＡＨＦ对阻力血管的影响明显高于容量血管，而ＴＭＰ对两种血管的ｃＧＭＰ水平影响无明显差异，ＡＨＦ与ＴＭＰ对血管ｃＧＭＰ的增高作用似乎与内皮无关。     

低硒低维生素E诱导肝细胞凋亡及cAMP和细胞内Ca2+的作用

目的 研究低硒（Ｓｅ）低维生素Ｅ（ＶＥ）能否诱导大鼠肝细胞凋亡及ｃＡＭＰ和细胞内Ｃａ＾２＋所起的作用。方法 以天然的和人工半合成的低Ｓｅ低ＶＥ饲料喂养大鼠１７周,采用流式细胞术检测肝细胞凋亡,采用放免法检测ｃＡＭＰ含量,Ｆｕｒａ－２负载荧光分光光度法测定细胞内Ｃａ＾２＋含量。结果 与补Ｓｅ和ＶＥ组大鼠相比,低Ｓｅ低ＶＥ组大鼠肝细胞凋亡显著增加;ｃＡＭＰ含量明显升高;细胞内Ｃａ＾２＋含量明显升高。结     

温胃舒冲剂对小鼠慢性萎缩性胃炎的保护作用及其机…

温胃舒冲剂是根据临床实践组成的中药复方制剂，为了探讨其作用机理，用小鼠造成３种模型：去氧胆酸钠（ＤＯＣＡ）造成慢性萎缩性胃炎（ＣＡＧ）模型；ＤＯＣＡ＋甲疏基咪唑造成ＣＡＧ－阳虚模型，ＤＯＣＡ＋甲状腺＋利血平造成ＣＡＧ－阴虚模型。以血浆中环磷酸腺苷（ｃＡＭＰ）、环磷酸鸟苷（ｃＧＭＰ）观察其治疗作用。结果表明，温胃舒能降低ＣＡＧ模型小鼠的ｃＡＭＰ、ｃＧＭＰ，也能降低ＣＡＧ－阳虚模型小鼠的ｃＧＭＰ，与模     

Production and role of extracellular guanosine cyclic 3', 5' monophosphate in sodium uptake in human proximal tubule cells

The present study was designed to determine the capability of human renal proximal tubule (RPT) to generate and export guanosine cyclic 3', 5' monophosphate (cGMP) in response to direct stimulation of soluble guanylyl cyclase by nitric oxide (NO) donors. In addition, we investigated whether cGMP extrusion from human RPT cells is required for inhibition of cellular sodium uptake. RPT cells were cultured from fresh human kidneys (normotensive subjects, n=4, mean age 65+/-4.7 years, 3 men, 1 woman; hypertensive patients, n=6, mean age 64+/-6.1 years, 4 men, 2 women) after unilateral nephrectomy. The fluorescence dye Sodium Green was employed to determine cytoplasmic Na+ concentration. In the presence of the Na+/K+ ATPase inhibitor ouabain, fluorescence was monitored at the appropriate wavelength (excitation 485 nm, emission 535 nm). Nitric oxide donor, S-nitroso-N-acetylpenicillamine (SNAP, 10(-4) M), increased both intracellular and extracellular cGMP (from 1.26+/-0.21 to 88.7+/-12.6 pmol/mg protein and from 0.58+/-0.10 to 9.24+/-1.9 pmol/mL, respectively, P<0.01) and decreased cellular Na+ uptake by 37.4+/-6.8% (P<0.05) compared with control. The effects of SNAP on cGMP production were similar in normotensive and hypertensive subjects. The increases in intracellular and extracellular cGMP concentration because of SNAP were blocked completely by soluble guanylyl cyclase inhibitor ODQ (1-H-[1,2,4] oxadiazolo [4,2-alpha] quinoxalin-1-one). Probenecid, an organic anion transport inhibitor, augmented the SNAP (10(-6) M)-induced increase in intracellular cGMP accumulation (from 4.9+/-0.9 to 9.8+/-1.5 pmol/mg protein, P<0.05), abrogated the SNAP-induced increase in extracellular cGMP extrusion (from 1.07+/-0.4 to 0.37+/-0.1 pmol/L, P<0.05) and blocked the SNAP-induced reduction in cellular Na+ uptake. Neither intracellular nor extracellular cGMP were influenced by l-arginine, the metabolic precursor of NO, or N(G)-nitro-L-arginine methyl ester, an inhibitor of NO synthase. After exogenous administration of cGMP (10(-5) M) or its membrane-permeable analogue 8-Br-cGMP (10(-5) M), only 8-Br-cGMP crossed the cell membrane to increase intracellular cGMP (from 1.36+/-0.19 to 289.7+/-29.4 pmol/mg protein, P<0.01). However, both cGMP and 8-Br-cGMP were effective in decreasing cellular Na+ uptake. In conclusion, human RPT cells contain soluble guanylyl cyclase and are able to generate and export cGMP in response to NO. Because human RPT cells do not themselves contain constitutive NO synthase, the NO-generating cGMP must be derived from sources outside the human RPT. The cGMP cellular export system is critical in the regulation of RPT cellular Na+ absorption in humans.     

Insulin increases NADH/NAD+ redox state, which stimulates guanylate cyclase in vascular smooth muscle

BACKGROUND: Insulin inhibits contraction and migration of primary confluent, cultured canine vascular smooth muscle cells (VSMCs) with inducible nitric oxide synthase (iNOS) by stimulating cyclic GMP (cGMP) production. The present study was performed to determine how insulin stimulates guanylate cyclase activity in these cells. METHODS: Primary cultured VSMC were obtained from canine femoral arteries. Lactate and pyruvate levels were measured by enzymatic assays, cGMP production by radioimmunoassay, iNOS activity by conversion of arginine to citrulline, and cell contraction by photomicroscopy. RESULTS: Insulin (1 nmol/L) increased cGMP production fivefold in VSMC with iNOS while raising the lactate-to-pyruvate ratio (LPR) from 3.1 +/- 0.5 to 10.0 +/- 1.6 (P < .05), indicating a rise in the ratio of reduced/oxidized nicotinamide adenine dinucleotide (NADH/NAD+) redox state of the cell. Insulin's stimulation of cGMP production was blocked by 0.1 mmol/L NG-monomethyl-L-arginine (L-NMMA) indicating dependence on iNOS activity, but insulin did not affect iNOS activity. Blocking insulin's increase in LPR by pyruvate (0.5 mmol/L) or oxaloacetate (0.5 mmol/L) completely inhibited the insulin-stimulated component of cGMP production. Pyruvate also blocked insulin's inhibition of serotonin-induced contraction in nonproliferated cells. In the absence of insulin, 5 mmol/L lactate or isocitrate increased the LPR by 420% +/- 47% and 167% +/- 20%, respectively (both P < .05), and stimulated cGMP production by 1,045% +/- 272% and 278% +/- 33%, respectively (both P < .05) by an L-NMMA-inhibitable mechanism. Although cGMP production in cells with iNOS was increased by insulin, the stimulation of cGMP production in cells without iNOS by 3-(5'-hydroxymethyl-2'furyl)-1-benzyl indazole (YC-1) was not affected by insulin, suggesting that insulin does not stimulate guanylate cyclase activity directly. CONCLUSION: We conclude that insulin increases cGMP production in VSMC with iNOS by raising the cell NADH/NAD+ redox state, which may increase the availability of iNOS-derived NO.     

Influence of metabolic control of insulin-dependent diabetes on plasma nucleotide levels (cAMP, cGMP) during bicycle exercise

Plasma concentrations of cyclic nucleotides (cAMP, cGMP) were measured before and during bicycle exercise in 8 well-controlled (mean pre-exercise blood glucose 5.3 mmol/l; HbA1 8.6%) and 8 moderately controlled (mean pre-exercise blood glucose 12.2 mmol/l; HbA1 10.8%) patients aged 18-32 years with insulin-dependent diabetes mellitus (IDDM) and in a group of non-diabetic control subjects matched for age and sex. Pre-exercise plasma cAMP concentrations and the rise with exercise were similar in all study groups. Significantly lower resting cGMP levels were found in well-controlled IDDM patients (3.5 +/- 0.3 pmol/ml, mean +/- SEM) compared to controls (5.6 +/- 1.1 pmol/ml; p less than 0.05) and moderately controlled IDDM patients (5.6 +/- 1.0 pmol/ml; p less than 0.05). By contrast, plasma cGMP levels increased during exercise in the diabetics but not in the controls. These findings indicate a significant difference in responses of plasma cGMP to exercise between IDDM patients and controls.     

Insulin-inhibited and stimulated cultured vascular smooth muscle cell migration are related to divergent effects on protein phosphatase-2A and autonomous calcium/calmodulin-dependent protein kinase II

Insulin, in the permissive presence of nitric oxide (NO), stimulates cGMP production which inhibits autonomous calcium/calmodulin-dependent protein kinase II (CaM kinase II) thereby inhibiting cultured vascular smooth muscle cell (VSMC) migration. In the presence of angiotensin II (Ang II), insulin stimulates NAD(P)H oxidase activity leading to increased VSMC migration. We wished to see whether insulin-stimulated cGMP stimulates protein phosphatase-2A (PP-2A) thereby inhibiting autonomous CaM kinase II and migration, and whether insulin, in the presence of Ang II, inhibits PP-2A and stimulates autonomous CaM kinase II in a NAD(P)H oxidase-dependent manner. One nanomole per litre of insulin in the presence of NO, or 50 micromol/L 8-Br-cGMP stimulated PP-2A activity by 46+/-6 and 247+/-23%, respectively (both P<0.05), and 8-Br-cGMP inhibited autonomous CaM kinase II activity by 67+/-9% (P<0.05) by a 10 nmol/L okadaic acid-sensitive pathway. Insulin plus Ang II inhibited PP-2A activity by 57+/-7% (P<0.05) and stimulated autonomous CaM kinase II activity by 120+/-14% (P<0.05), both by an apocynin-sensitive pathway. 8-Br-cGMP-inhibited VSMC migration was blocked by okadaic acid. It is concluded that insulin in the presence of NO stimulates cGMP which stimulates PP-2A activity causing inhibition of autonomous CaM kinase II activity and thus VSMC migration, and that insulin in the presence of Ang II inhibits PP-2A and stimulates autonomous CaM kinase II activities by a NAD(P)H oxidase-dependent mechanism which are associated with insulin-stimulated NAD(P)H oxidase-dependent migration.     

Cinacalcet and the prevention of secondary hyperparathyroidism in rats with aldosteronism

BACKGROUND: In rats receiving aldosterone/salt treatment (ALDOST), increased Ca2+ excretion leads to a fall in plasma-ionized Ca2+ and appearance of secondary hyperparathyroidism (SHPT) with parathyroid hormone (PTH)-mediated intracellular Ca2+ overloading inducing oxidative stress in diverse tissues. Parathyroidectomy prevents this scenario. Rats with ALDOST were cotreated with cinacalcet (Cina), a calcimimetic that raises the threshold of the parathyroids' Ca(2+)-sensing receptor. METHODS AND RESULTS: We monitored plasma-ionized [Ca2+]o, PTH, and total Ca2+ in heart and peripheral blood mononuclear cells (PBMC), and evidence of oxidative stress in heart, PBMC, and plasma. Cina-treated rats for 4 weeks were compared with 4 weeks of ALDOST alone and with untreated age-/gender-matched controls. In comparison to controls, ALDOST led to a fall (P < 0.05) in Ca2+ (1.16 +/- 0.01 vs 1.03 +/- 0.01 mmol/L), which was not prevented by Cina (1.01 +/- 0.03 mmol/L); a rise (P < 0.05) in plasma PTH (36 +/- 7 vs 134 +/- 19 pg/mL) that was attenuated by Cina (69 +/- 12 pg/mL); increased (P < 0.05) cardiac [Ca2+] (3.92 +/- 0.25 vs 6.78 +/- 0.35 nEq/mg FFDT) and PBMC [Ca2+]i (29.8 +/- 2.3 vs 50.2 +/- 2.3 nmol/L), each of which was prevented with Cina (3.65 +/- 0.10 nEq/mg FFDT and 32.5 +/- 6.0 nmol/L, respectively); increased cardiac MDA (0.56 +/- 0.03 vs 0.94+/-0.07 nmol/mg protein) and PBMC H2O2 production (63.5 +/- 7.5 vs 154.0 +/- 25.2 mcb) and reduced (P < 0.05) plasma alpha1-AP activity (39.8 +/- 0.6 vs 29.6 +/- 1.8 mM), each prevented by Cina (0.66 +/- 0.04 mmol/mg protein, 58.2 +/- 12.7 mcb and 37.0 +/- 1.2 mM, respectively). CONCLUSIONS: PTH-mediated intracellular Ca2+ overloading accounts for the induction of oxidative stress in diverse tissues in rats with aldosteronism and which can be prevented by Cina.     

Insulin influences the nitric oxide cyclic nucleotide pathway in cultured human smooth muscle cells from corpus cavernosum by rapidly activating a constitutive nitric oxide synthase

AIMS: We have evaluated, in cultured human cavernosal smooth muscle cells, the expression and activity of calcium-dependent constitutive nitric oxide synthase (cNOS) and the ability of insulin to induce nitric oxide (NO) production and to increase intracellular cyclic nucleotides guanosine 3',5'-cyclic monophosphate (cGMP) and adenosine 3',5'-cyclic monophosphate (cAMP). METHODS: cNOS mRNA was detected by RT-PCR amplification, cNOS protein by immunofluorescence, cNOS activity as l-[3H]-citrulline production from l-[3H]-arginine and cyclic nucleotides by radioimmunoassay. RESULTS: cNOS mRNA and cNOS protein were found in cultured cells; cNOS activity was increased by 5-min exposure to 1 micro mol/l calcium ionophore ionomycin (from 0.1094+/-0.0229 to 0.2685+/-0.0560 pmol/min per mg cell protein, P=0.011) and to 2 nmol/l insulin (from 0.1214+/-0.0149 to 0.2045+/-0.0290 pmol/min per mg cell protein, P=0.041). Insulin increased both cGMP and cAMP in a dose- and time-dependent manner (i.e. with 2 nmol/l insulin, cGMP rose from 2.71+/-0.10 to 6.80+/-0.40 pmol/10(6) cells at 30 min, P=0.0001; cAMP from 1.26+/-0.06 to 3.02+/-0.30 pmol/10(6) cells at 60 min, P=0.0001). NOS inhibitor N(G)-monomethyl-l-arginine and phosphatidylinositol 3-kinase (PI 3-kinase) inhibitors wortmannin and LY 294002 blunted these effects of insulin. The action of insulin on cyclic nucleotides persisted in the presence of phosphodiesterase inhibition, guanylate cyclase activation by NO donors and adenylate cyclase activation by Iloprost or forskolin. CONCLUSION: Human cavernosal smooth muscle cells, by expressing cNOS activity, are a source of NO and not only its target; in these cells, insulin rapidly activates cNOS through a PI 3-kinase pathway, with a consequent increase of both cyclic nucleotides, thus directly influencing the mechanisms involved in penile vascular tone and interplaying with classical haemodynamic mediators.     

Hormonal and metabolic responses during coronary artery bypass surgery: role of infused glucose

Anesthesia, surgery, and hypothermia are conventionally considered the major stress factors in the metabolic and hormonal responses to cardiac surgery. We compared these responses in 14 nondiabetics during and for 24 h after coronary artery bypass surgery; 8 received cardioplegic solutions (C+), and 6 did not (C-). The mean intraoperative glucose load in C+ was 106 g compared to 32 g in C-; postoperatively both groups received 50 g. Marked hyperglycemia (31.8 +/- 4.8 mmol/L) occurred during hypothermia in C+, but dropped to 18.9 mmol/L before surgery ended and to 11.2 +/- 1.1 mmol/L by 2 h postop. In contrast, C- showed constant mild hyperglycemia of 8.3-9.8 mmol/L throughout, significantly less than C+ until 1 h postop. Insulin was suppressed by 55% only during hypothermia, peaking with rewarming in C+ at 2,849 +/- 911 vs. 639 +/- 251 pmol/L in C- (P less than 0.05); as with glycemia, values were comparable after 2 h postop. The pancreatic beta-cell thus responded to hyperglycemia during restoration of normothermia, resulting in a rapid decline in glycemia. This occurred despite elevations in antiinsulin factors in both groups; GH was 14 +/- 4 micrograms/L, cortisol was 607 +/- 38.6 nmol/L, norepinephrine was 11.5 +/- 3.7 nmol/L, epinephrine was 13,863 +/- 3,875 pmol/L, and FFA were 0.36 +/- 0.05 g/L. Early postop, a secondary rise in stress hormones occurred in both groups. Maximal cortisol values were at 4 h (1,186 +/- 140 nmol/L) and peaks of norepinephrine (6.50 +/- 1.66 nmol/L), epinephrine (7,969 +/- 3,602 pmol/L), and FFA (0.27 +/- 0.03 g/L) occurred. The only significant glucagon elevation was at 24 h (C+, 464 +/- 53 ng/L; C-, 350 +/- 241 ng/L; P less than 0.02), Thus, 1) many metabolic responses during coronary artery bypass surgery are influenced by the glucose-containing cardioplegic solution; 2) hypothermia suppresses insulin secretion, but it responds thereafter despite marked elevations of catecholamines, and is associated with decreasing glycemia despite elevated antiinsulin factors; 3) a lesser but highly significant stress response corresponds to awakening from anesthesia; and 4) glucagon plays a minor role in intraoperative hyperglycemia; the rise at 24 h is unexplained.     

Activation of Ca(2+)-independent nitric oxide synthase by 17beta-estradiol in post-ischemic rat heart

BACKGROUND: Nitric oxide (NO) donors or facilitation of endogenous NO production is cardioprotective. This study sought to determine whether enhanced myocardial NO production might contribute to estrogen-induced cardioprotection. METHODS: Ca(2+)-dependent and Ca(2+)-independent NOS activities (pmol min(-1) mg(-1) protein), NOS protein expression (quantitative immunoblot), cGMP content (pmol mg(-1) protein) and LV work (Joules) were measured in hearts isolated from ovariectomized rats that were either untreated or treated chronically with 17beta-estradiol (0.25 mg, 21 day release formulation). RESULTS: After 14 days, serum levels of 17beta-estradiol were 6+/-1 and 135+/-16 pg ml(-1) in untreated and 17beta-estradiol-treated animals, respectively. After 60 min aerobic working mode perfusion, Ca(2+)-dependent NOS (untreated, 1.47+/-0.36; 17beta-estradiol 1.13+/-0.25) and Ca(2+)-independent NOS (untreated, 0.45+/-0.24; 17beta-estradiol, 0.41+/-0.21) activities, eNOS and iNOS proteins and cGMP content (untreated, 0.64+/-0.08; 17beta-estradiol, 0.76+/-0.12) were not different in the two groups. After 60 min low-flow (0.5 ml min(-1)) ischemia and 30 min reperfusion, Ca(2+)-dependent NOS activities were again similar (untreated, 1.25+/-0.23; 17beta-estradiol, 0.78+/-0.27). However, after reperfusion, Ca(2+)-independent NOS activity (untreated, 0. 39+/-0.10; 17beta-estradiol, 1.36+/-0.36) was 3.5-fold higher (P=0. 008) and cGMP content (untreated, 0.30+/-0.03; 17beta-estradiol, 0. 49+/-0.07) was 1.6-fold higher (P=0.017) in hearts from 17beta-estradiol-treated animals. Although pre-ischemic function was similar, recovery of post-ischemic LV work was 2-fold greater (P=0.024) in the 17beta-estradiol group. CONCLUSION: The ability of ischemia and reperfusion in combination with chronic 17beta-estradiol to increase Ca(2+)-independent NOS activity and cGMP content supports a role for enhanced myocardial NO signaling in 17beta-estradiol-induced cardioprotection.     

Rapid stimulation of L-arginine transport by D-glucose involves p42/44(mapk) and nitric oxide in human umbilical vein endothelium

D-glucose infusion and gestational diabetes induce vasodilatation in humans and increase L-arginine transport and nitric oxide (NO) synthesis in human umbilical vein endothelial cells. High D-glucose (25 mmol/L, 2 minutes) induced membrane hyperpolarization and an increase of L-arginine transport (V(max) 6.1+/-0.7 versus 4.4+/-0.1 pmol/ microg protein per minute) with no change in transport affinity (K(m) 105+/-9 versus 111+/-16 micromol/L). L-[3H]citrulline formation and intracellular cGMP, but not intracellular Ca2+, were increased by high D-glucose. The effects of D-glucose were mimicked by levcromakalim (ATP-sensitive K+ channel blocker), paralleled by p42/p44(mapk) and Ser(1177)-endothelial NO synthase phosphorylation, inhibited by N(G)-nitro-L-arginine methyl ester (L-NAME; NO synthesis inhibitor), glibenclamide (ATP-sensitive K+ channel blocker), KT-5823 (protein kinase G inhibitor), PD-98059 (mitogen-activated protein kinase kinase 1/2 inhibitor), and wortmannin (phosphatidylinositol 3-kinase inhibitor), but they were unaffected by calphostin C (protein kinase C inhibitor). Elevated D-glucose did not alter superoxide dismutase activity. Our findings demonstrate that the human fetal endothelial L-arginine/NO signaling pathway is rapidly activated by elevated D-glucose via NO and p42/44(mapk). This could be determinant in pathologies in which rapid fluctuations of plasma D-glucose may occur and may underlie the reported vasodilatation in early stages of diabetes mellitus.