咪达唑仑对人肺脏液体清除的作用机制研究

目的探讨咪达唑仑对人肺上皮细胞短路电流的影响,并探讨可能的机制。方法应用尤斯灌流室装置测定H441单层细胞的短路电流。由总电流减去阿米洛利可抑制的电流算得阿米洛利敏感性电流,以用药前H441单层细胞的阿米洛利敏感性电流初始值为100%对照。用100μmol/L咪达唑仑处理H441细胞,在0,15,30,60min 4个时间点提取蛋白用于蛋白印迹法,研究咪达唑仑对细胞外调节蛋白酶(ERK)1/2蛋白磷酸化的影响。结果咪达唑仑能够剂量依赖性抑制H441单层细胞的短路电流,此电流可被阿米洛利抑制;蛋白印迹法结果显示咪达唑仑能够促进ERK1/2蛋白磷酸化。结论咪达唑仑通过抑制人肺上皮细胞阿米洛利敏感性电流而降低肺泡上皮离子转运,其机制可能与其促进ERK1/2蛋白磷酸化有关。临床上对伴有肺水肿的患者应用咪达唑仑时应考虑其可能对肺泡上皮液体清除的影响。     

布比卡因对人肺上皮细胞短路电流影响的研究

目的布比卡因是长效酰胺类局麻药,本研究旨在观察布比卡因对人肺上皮细胞短路电流的影响,并探讨可能的机制。方法应用尤斯灌流室装置测定H441单层细胞的短路电流。由总电流减去阿米洛利抑制后的电流算得阿米洛利敏感性电流,以用药前H441单层细胞的阿米洛利敏感性电流初始值为100%对照。用100μmol·L~(-1)布比卡因处理H441细胞,在0、15、30、60 min 4个时间点提取蛋白用于Western blot,研究布比卡因对ERK1/2蛋白磷酸化的影响。结果布比卡因能够剂量依赖性抑制H441单层细胞的短路电流,此电流可被阿米洛利抑制;Western blot结果显示,布比卡因能够促进ERK1/2蛋白磷酸化。结论布比卡因通过抑制人肺上皮细胞阿米洛利敏感性电流而降低肺泡上皮离子转运,其机制可能与其促进ERK1/2蛋白磷酸化有关。临床上对伴有肺部疾患的病人应用布比卡因时应考虑其可能对肺泡上皮液体清除的影响。     

巴豆醛对小鼠气管短路电流的影响及相关机制研究

目的探讨巴豆醛对小鼠气管上皮及原代培养单层气管上皮细胞短路电流的影响及其与PKG2之间的关系,明确巴豆醛在呼吸系统液体转运中可能的作用机制。方法应用尤斯灌流装置记录小鼠气管上皮及原代培养单层气管上皮细胞短路电流,采用Elisa实验明确巴豆醛对ENa C活性的影响。结果巴豆醛能够抑制小鼠气管上皮和原代培养的单层气管上皮细胞的阿米洛利敏感性短路电流,而此阿米洛利敏感性肺液清除主要是由ENa C介导的液体转运。Elisa实验进一步明确了巴豆醛通过抑制PKG2而参与ENa C活性的调控作用。结论巴豆醛可能通过抑制呼吸系统ENa C的功能,阻碍Na+的重吸收,通过抑制PKG2而参与ENa C活性的调控作用,进而诱导产生肺水肿或急性呼吸窘迫综合征。     

钾通道在维拉帕米抑制上皮钠通道中的作用

目的探讨钾通道在维拉帕米引起的肺水肿中的作用。方法应用尤斯灌流室技术检测钾通道阻滞剂对维拉帕米抑制上皮钠通道的作用。Clofilium,clotrimazole以及glibenclamide(分别为KvLQT1,KCa和KATP通道的阻滞剂)加入H441单层细胞基底侧后,记录短路电流。同时,在穿孔细胞层中观察了维拉帕米对Na+/K+泵的作用。结果在穿孔H441细胞层中观察到维拉帕米对上皮钠通道和Na+/K+泵均有抑制作用。Clofilium,clotri mazole以及glibenclamide分别抑制短路电流至54.4±4.6%,32.1±5.2%,和20.5±1.1%(n=5)。用上述三种钾通道阻滞剂预处理后,维拉帕米对短路电流的作用由对照组的45.9±4.8%分别降低至23.7±4.3%,34.2±2.6%和36.0±2.8%(n=4)。Clofilium显示了对短路电流的最大抑制,与其它两种抑制剂相比具有统计学差异。应用clofilium后加入维拉帕米与对照组相比,其抑制率具有明显统计学差异(P<0.05)。结论这些结果表明KCa,KATP,尤其是KvLQT1通道在肺上皮细胞维拉帕米引起的非心源性肺水肿的Na+和Cl-转运的病理生理过程中发挥重要作用。     

羧甲基壳聚糖对肺泡液体清除率的作用研究

目的探讨羧甲基壳聚糖与肺泡液体清除率(Alveolar fluid clearance,AFC)之间的关系,阐明羧甲基壳聚糖是否参与了肺上皮液体转运。方法应用酶标仪测定小牛血清白蛋白浓度的方法测定小鼠在体AFC。结果羧甲基壳聚糖气管内给药对AFC无明显抑制作用。结论羧甲基壳聚糖可能不影响肺泡上皮钠主动转运机能,抑制肺水肿液的吸收。     

羧甲基壳聚糖对大鼠单一心室肌细胞ATP敏感钾电流的作用

目的 研究羧甲基壳聚糖对大鼠单一心宣肌细胞ATP敏感钾电流(IkAIP)的作用.方法 急性分离大鼠心室肌细胞,利用膜片钳削技术全细胞记录法,保持电位-40mV,指令电位-100～ 50mV,步阶脉冲10mV,波宽200ms,刺激间隔6s的方波钳制方案进行刺激.结果 羧甲基壳聚糖抑制心室肌细胞IKATP,且具有剂量依赖关系.指令电位在 50mV时,3种浓度羧甲基壳聚糖(0.1%,0.2%,0.3%)可使IKATP分别降低至给药前的66.1%±9.9%,50.3%±13.3%和39.8%±9.5%(n=7).其它指令电位下的IKATP改变也符合此趋势.结论 羧甲基壳聚糖剂量依赖性地抑制大鼠单一心室肌细胞IKATP,这可能是其抗心律失常的机制之一.     

纤溶酶对小鼠肺泡上皮液体清除作用的研究

目的探讨纤溶酶对在体小鼠肺泡液体清除率(AFC)的作用。方法应用考马斯亮蓝法测定小牛血清白蛋白浓度的方法测定小鼠在体AFC。结果特异性上皮细胞钠通道阻断剂阿米洛利组能明显降低AFC,气管内注入60μg/mL纤溶酶后,AFC明显增加(38.2±2.1)%,与对照组相比P<0.05,n=6)。纤溶酶+阿米洛利组对AFC的影响与对照组相比差异无统计学意义(P>0.05,n=5),与单独使用纤溶酶比较差异有统计学意义(P<0.05)。结论纤溶酶能明显增加肺泡上皮液体的清除,可能通过增强阿米洛利敏感性钠通道活性而影响AFC。     

羧甲基壳聚糖-Co(II)配合物与鲱鱼精DNA的相互作用

目的 研究了羧甲基壳聚糖-Co(II)配合物与鲱鱼精DNA之间的作用方式。方法 采用循环伏安法和光谱法研究了羧甲基壳聚糖-Co(II)配合物与鲱鱼精DNA之间的作用机制。结果 (1) 羧甲基壳聚糖-Co(II)的存在导致Fe(CN)63-/4-探针分子氧化还原峰电流下降,峰值电位正移,显示羧甲基壳聚糖-Co(II)和Fe(CN)63-/4-与DNA之间存在竞争性作用。(2) 随着DNA的不断加入,羧甲基壳聚糖-Co(II)的特征吸收峰强度逐渐降低,峰位红移;同时,中性红的加入导致羧甲基壳聚糖-Co(II)/DNA体系的特征吸收峰发生增色效应、峰位红移并伴有等吸收点出现,表明羧甲基壳聚糖-Co(II)、DNA与中性红三者存在新的共平衡体系,中性红对羧甲基壳聚糖-Co(II)与DNA的作用有竞争抑制作用。结论 羧甲基壳聚糖-Co(II)能够以嵌插方式与鲱鱼精DNA发生相互作用。     

羧甲基壳聚糖对大鼠心室肌细胞钠电流的影响

目的研究羧甲基壳聚糖对大鼠心室肌细胞钠电流(I_(Na))的作用,在离子通道水平探讨羧甲基壳聚糖的抗心律失常作用机制。方法急性分离大鼠心室肌细胞,利用膜片钳制技术全细胞记录法,设保持电位为-120mV,指令电位为-80～+20 mV,步阶脉冲10 mV,波宽50 ms,刺激间隔2 s的方波钳制方案进行刺激。结果羧甲基壳聚糖抑制心室肌细胞I_(Na),且具有剂量依赖性关系。3种浓度(0.1%,0.2%,0.3%)羧甲基壳聚糖可使I_(Na)电流密度峰值分别降低至给药前的57.4%±6.7%,40.9%±5.4%和16.1%±4.3%(P<0.01,n=7)。结论羧甲基壳聚糖剂量依赖性的抑制大鼠单一心室肌细胞I_(Na),这可能是其抗心律失常的机制之一。     

羧甲基壳聚糖抗肿瘤及免疫增强活性研究

目的:评价羧甲基壳聚糖抗肿瘤和免疫增强活性。方法:MTT法研究羧甲基壳聚糖体外活性,S180实体瘤模型用于评价羧甲基壳聚糖体内抗肿瘤活性,流式细胞术分析肿瘤细胞的周期变化和细胞凋亡,ELISA法测定羧甲基壳聚糖对免疫功能的调节。结果:羧甲基壳聚糖抑制肿瘤细胞增殖,IC_(50)为30μg/mL,肿瘤抑制率为27.9%～43.6%。用药后细胞周期阻滞在G_1期,肿瘤细胞凋亡明显增加。体内具有明显的抑瘤和免疫增强作用。结论:羧甲基壳聚糖可以通过直接杀伤肿瘤细胞和增强免疫而发挥抗肿瘤效应。     

Benzimidazolones enhance the function of epithelial Na+ transport

Background and Purpose

Pharmacological enhancement of vectorial Na⁺ transport may be useful to increase alveolar fluid clearance. Herein, we investigated the influence of the benzimidazolones 1-ethyl-1,3-dihydro-2-benzimidazolone (1-EBIO), 5,6-dichloro-1-EBIO (DC-EBIO) and chlorzoxazone on vectorial epithelial Na⁺ transport.

Experimental Approach

Effects on vectorial Na⁺ transport and amiloride-sensitive apical membrane Na⁺ permeability were determined by measuring short-circuit currents (I_SC) in rat fetal distal lung epithelial (FDLE) monolayers. Furthermore, amiloride-sensitive membrane conductance and the open probability of epithelial Na⁺ channels (ENaC) were determined by patch clamp experiments using A549 cells.

Key Results

I_SC was increased by approximately 50% after addition of 1-EBIO, DC-EBIO and chlorzoxazone. With permeabilized basolateral membranes in the presence of a 145:5 apical to basolateral Na⁺ gradient, the benzimidazolones markedly increased amiloride-sensitive I_SC. 5-(N-Ethyl-N-isopropyl)amiloride-induced inhibition of I_SC was not affected. The benzamil-sensitive I_SC was increased in benzimidazolone-stimulated monolayers. Pretreating the apical membrane with amiloride, which inhibits ENaC, completely prevented the stimulating effects of benzimidazolones on I_SC. Furthermore, 1-EBIO (1 mM) and DC-EBIO (0.1 mM) significantly increased (threefold) the open probability of ENaC without influencing current amplitude. Whole cell measurements showed that DC-EBIO (0.1 mM) induced an amiloride-sensitive increase in membrane conductance.

Conclusion and Implications

Benzimidazolones have a stimulating effect on vectorial Na⁺ transport. The antagonist sensitivity of this effect suggests the benzimidazolones elicit this action by activating the highly selective ENaC currents. Thus, the results demonstrate a possible new strategy for directly enhancing epithelial Na⁺ transport.     

Activation of epithelial Na(+) channel activity in the rabbit urinary bladder by cAMP

The rabbit urinary bladder actively absorbs Na(+) from the urine. The rate-limiting step in this process is the diffusion of Na(+) across the apical membrane of bladder epithelial cells, mediated by amiloride-sensitive epithelial Na(+) channels. We have investigated the effects of cAMP on epithelial Na(+) channel activity in the rabbit bladder by measuring the amiloride-sensitive short-circuit current across bladders mounted in Ussing chambers. Three agents that raise intracellular cAMP levels (forskolin, dibutyryl-cAMP and 3-isobutyl-1-methylxanthine (IBMX)) increased the amiloride-sensitive short-circuit current relative to control preparations. The forskolin-induced increase in amiloride-sensitive short-circuit current was significantly inhibited by the vesicle fusion inhibitor brefeldin A and the protein synthesis inhibitor cycloheximide. These findings, together with the magnitude and protracted time course of the cAMP effects, suggests that cAMP stimulates the insertion of new Na(+) channels into the apical membrane of the rabbit bladder epithelium.     

Growth inhibition of lung cancer cells by adenosine 5′‐triphosphate

Preliminary clinical data suggest that adenosine 5′‐triphosphate (ATP) may inhibit lung tumor growth. Because studies of ATP on lung cancer cells are lacking, the aim of the present study was to explore effects of extracellular ATP on the growth and morphology of human lung tumor cells. Five human lung tumor cell lines derived from tumors with different cellular characteristics, i.e., a small cell carcinoma (GLC4), a large cell carcinoma (H460), a squamous cell carcinoma (H520), a mesothelioma (MERO82), and a papillary adenocarcinoma (H441), were exposed to 0, 0.5, 1, 2, and 3 mM ATP. Total cell numbers and dead or damaged cells were measured on days 1, 2, and 3. ATP induced a significant, dose‐dependent growth inhibition in GLC4, H460, H520, and MERO82 cells. In contrast, H441 cells showed already maximal inhibition at 0.5 mM. Compared to untreated control cell lines, a significant growth inhibition (mean ± SEM) of 65 ± 5% (GLC4), 59 ± 5% (H460), 45 ± 5% (H520), 38±2% (MERO82), and 55 ± 8% (H441) was shown after 3 days incubation with 3 mM ATP. ATP also induced changes in morphology and attachment to the substratum. Although not demonstrated by the Trypan Blue exclusion test, on photographs it seems that ATP induces death of GLC4 and H460 cells at higher concentrations. In conclusion, in four out of five explored lung tumor cell lines, ATP induces a dose‐dependent growth inhibition. Lung adenocarcinoma cells show already maximal inhibition at the lowest tested ATP dose. There is a relationship between growth inhibition and morphology changes. Drug Dev. Res. 60:196–203, 2003. © 2003 Wiley‐Liss, Inc.     

Halothane directly modifies Na+ and K+ channel activities in cultured human alveolar epithelial cells

During inhalational anesthesia, halogenated gases are in direct contact with the alveolar epithelium, in which they may affect transepithelial ion and fluid transport. The effects of halogenated gases in vivo on epithelial Na+ and K+ channels, which participate in alveolar liquid clearance, remain unclear. In the present study, the effects of halothane (1, 2, and 4% atm) on ion-channel function in cultured human alveolar cells were investigated using the patch-clamp technique. After exposure to 4% halothane, amiloride-sensitive whole-cell inward currents increased by 84+/-22%, whereas tetraethylammonium-sensitive outward currents decreased by 63+/-7%. These effects, which occurred within 30 s, remained for 30-min periods of exposure to the gas, were concentration-dependent, and were reversible upon washout. Pretreatment with amiloride prevented 90+/-7% of the increase in inward currents without change in outward currents, consistent with an activation of amiloride-sensitive epithelial sodium channels. Tetraethylammonium obliterated 90+/-9% of the effect of halothane on outward currents, without change in inward currents, indicating inhibition of Ca2+-activated K+ channels. These channels were identified in excised patches to be small-conductance Ca2+-activated K+ channels. These effects of halothane were not modified after the inhibition of cytosolic phospholipase A2 by aristolochic acid. Exposure of the cells to either trypsin or to low Na+ completely prevented the increase in amiloride-sensitive currents induced by halothane, suggesting a release of Na+ channels self-inhibition. Thus, halothane modifies differentially and independently Na+ and K+ permeabilities in human alveolar cells.     

盐酸埃他卡林对动脉平滑肌钾电流的影响

目的　探讨抗高血压新药盐酸埃他卡林对动脉平滑肌细胞钾电流的作用。方法　分离大鼠动脉平滑肌细胞 ,用膜片钳全细胞记录技术记录细胞钾电流 ,通过浴槽内给药 ,观察盐酸埃他卡林对钾电流的影响。结果　盐酸埃他卡林(0 1、1、10、10 0 μmol·L-1)均可明显引起正常血压大鼠肺动脉平滑肌外向钾电流I U曲线上移 ,盐酸埃他卡林作用后 5min内细胞外向钾电流强度分别增强为初始电流强度的[(118 6± 15 9) % ,P <0 0 1vscontrol,n =6 ]、[(10 3 9±5 9) % ,P <0 0 1vscontrol,n =5 ]、[(132 7± 2 3 9) % ,P <0 0 1vscontrol,n =6 ]、[(15 0 1± 2 5 1) % ,P <0 0 1vscontrol,n =7];盐酸埃他卡林 (1、10、10 0 μmol·L-1)均可引起肾性高血压大鼠肺动脉平滑肌外向钾电流I U曲线上移 ,盐酸埃他卡林作用后 5min内细胞外向钾电流强度分别增强为初始电流强度的 [(12 1 5± 4 2 ) % ,P <0 0 1vscon trol,n =7]、[(132 2± 6 7) % ,P <0 0 1vscontrol,n =8]、[(114 2± 7 7) % ,P <0 0 1vscontrol,n =8];盐酸埃他卡林 (10 μmol·L-1)可引起肺动脉高压大鼠肺动脉平滑肌外向钾电流I U曲线上移 ,盐酸埃他卡林作用后 5min内细胞外向钾电流强度为初始电流强度的 [(80 6± 10 1) % ,n =5 ],同时间对照     

壳聚糖及其衍生物体外抗幽门螺杆菌作用及影响因素

目的研究壳聚糖及其衍生物在体外对幽门螺杆菌(Hp)的抑菌作用及其影响因素。方法采用打孔法检测了不同浓度、pH值、脱乙酰度壳聚糖及羧甲基壳聚糖在体外对Hp的抑菌作用。结果①壳聚糖和羧甲基壳聚糖在体外对3株Hp标准菌株具有普遍的抑菌作用;②在pH 6~4范围内,随pH值降低,抗菌作用增强,差异有显著性(P<0.01),最佳pH值为4;③70%、88.5%脱乙酰度壳聚糖及羧甲基壳聚糖的抗Hp作用差异有显著性(P<0.01~0.05),抑菌强度依次为DD70壳聚糖、DD88.5壳聚糖和羧甲基壳聚糖;④在质量浓度为10 g.L-1~50 g.L-1范围内羧甲基壳聚糖抗Hp作用差异无显著性;在质量浓度为5 g.L-1~20 g.L-1范围内70%、88.5%脱乙酰度壳聚糖抗Hp作用差异也无显著性(P>0.05)。结论①壳聚糖和其衍生物对Hp有普遍的抑菌作用;②壳聚糖及其衍生物的抗Hp作用受多种因素影响,其中pH值对壳聚糖抗菌作用的影响最为明显,在pH值6~4范围内,壳聚糖的抗菌活性随着pH值的下降而增强;③壳聚糖的脱乙酰度、结构(化学修饰)及分子量也影响壳聚糖的抗菌活性,不同的细菌所要求的脱乙酰度、修饰基团和分子量有着明显的差异。     

Regulation of Na+ channel density at the apical surface of rabbit urinary bladder epithelium

We have investigated the effects of various manipulations on Na(+) transport across the rabbit urinary bladder epithelium. After bladders were mounted in Ussing chambers there was a spontaneous and significant (>4-fold) increase in amiloride-sensitive short-circuit current (equivalent to net Na(+) transport) over a 6-h period. The increase in current was almost abolished by brefeldin A, an inhibitor of anterograde vesicular transport, and reduced after a 3-h delay by cycloheximide, an inhibitor of protein synthesis. The spontaneous increase in short-circuit current was potentiated by treatment of bladders with either forskolin, which causes an elevation in cAMP levels, or aldosterone. Acting together, these two agents produced a significant synergistic effect on short-circuit current. The short-circuit current recovered rapidly after reduction in intracellular Na(+) levels, achieved either by lowering the extracellular Na(+) concentration or blockade of epithelial Na(+) channels with the sulphydryl modifying reagent p-chloromercuribenzenesulphonic acid (PCMBS). Recovery after PCMBS treatment was partially sensitive to brefeldin A. Short-circuit current saturated as the extracellular Na(+) concentration was increased (EC(50) = 51 mM). Saturation occurred over a range of Na(+) concentrations in which single channel permeability is known to remain constant, indicating that it depends on a reduction in epithelial Na(+) channel density at the apical plasma membrane. Exposure of bladders to a high Na(+) concentration caused an increase in endocytotic activity, detected through an increase in the uptake of the fluid-phase marker fluorescein isothiocyanate (FITC)-dextran into vesicles located beneath the apical plasma membrane. We conclude that the urinary bladder epithelium is able to respond rapidly and efficiently to changes in its environment by regulating the density of epithelial Na(+) channels in its apical surface.     

REDUCED LUNG WATER TRANSPORT RATE ASSOCIATED WITH DOWNREGULATION OF AQUAPORIN-1 AND AQUAPORIN-5 IN AGED MICE

• 1 The purpose of the present study was to examine lung water transport properties and the expression and regulation of the alveolar endothelial water channel aquaporin (AQP)‐1 and the epithelial water channel AQP‐5 in aged mouse lung using gene expression analysis and water permeability measurements.
• 2 In aged (20–24‐month‐old) mice, AQP‐1 and AQP‐5 mRNA expression decreased by 55.5 and 50.3%, respectively, compared with that in young (8–10‐week‐old) mice (P < 0.01). In addition, AQP‐1 and AQP‐5 protein expression decreased in aged mice by 36.9 and 44.6%, respectively, compared with that in young mice (P < 0.01).
• 3 The osmotically driven water transport rate between the airspace and capillary compartments was reduced by 31.7% in aged mice compared with young mice (2.8 ± 0.3 vs 4.1 ± 0.3 mg/s, respectively; P < 0.01). The hydrostatically driven lung water accumulation rate in response to a 10 cmH₂O increase in pulmonary artery pressure was also reduced in aged mice by 21.9% compared with young mice (0.32 ± 0.06 vs 0.41 ± 0.04 mg/s, respectively; P < 0.01).
• 4 There was a 62.7% decrease in serum glucocorticoids in aged mice compared with young mice (67.6 ± 26.8 vs 181.3 ± 44.4 nmol/L, respectively; P < 0.01). In vivo administration of dexamethasone (4 mg/kg) for 5 consecutive days to aged mice increased lung AQP‐1 mRNA and protein expression by 2.1 ± 0.1 fold (P < 0.01) and 1.8 ± 0.2 fold (P < 0.01), respectively. Accordingly, osmotically and hydrostatically driven water transport rates increased by 35.6% (P < 0.01) and 31.2% (P < 0.01), respectively.
• 5 The present study provides the first evidence of altered lung water transport associated with downregulation of AQPs in aged lung. Blood glucocorticoid hormone levels are important to maintain normal AQP‐1 expression in the lung microvascular endothelium. Corticosteroid‐induced AQP‐1 upregulation may contribute to the role of corticosteroids in accelerating oedema clearance in aged lung.

     

The gasotransmitter hydrogen sulphide decreases Na⁺ transport across pulmonary epithelial cells

BACKGROUND AND PURPOSE The transepithelial absorption of Na(+) in the lungs is crucial for the maintenance of the volume and composition of epithelial lining fluid. The regulation of Na(+) transport is essential, because hypo- or hyperabsorption of Na(+) is associated with lung diseases such as pulmonary oedema or cystic fibrosis. This study investigated the effects of the gaseous signalling molecule hydrogen sulphide (H(2) S) on Na(+) absorption across pulmonary epithelial cells. EXPERIMENTAL APPROACH Ion transport processes were electrophysiologically assessed in Ussing chambers on H441 cells grown on permeable supports at air/liquid interface and on native tracheal preparations of pigs and mice. The effects of H(2)S were further investigated on Na(+) channels expressed in Xenopus oocytes and Na(+) /K(+)-ATPase activity in vitro. Membrane abundance of Na(+) /K(+)-ATPase was determined by surface biotinylation and Western blot. Cellular ATP concentrations were measured colorimetrically, and cytosolic Ca(2+) concentrations were measured with Fura-2. KEY RESULTS H(2)S rapidly and reversibly inhibited Na(+) transport in all the models employed. H(2)S had no effect on Na(+) channels, whereas it decreased Na(+) /K(+)-ATPase currents. H(2)S did not affect the membrane abundance of Na(+) /K(+)-ATPase, its metabolic or calcium-dependent regulation, or its direct activity. However, H(2)S inhibited basolateral calcium-dependent K(+) channels, which consequently decreased Na(+) absorption by H441 monolayers. CONCLUSIONS AND IMPLICATIONS H(2) S impairs pulmonary transepithelial Na(+) absorption, mainly by inhibiting basolateral Ca(2+)-dependent K(+) channels. These data suggest that the H(2)S signalling system might represent a novel pharmacological target for modifying pulmonary transepithelial Na(+) transport.     

Brain targeting studies on buspirone hydrochloride after intranasal administration of mucoadhesive formulation in rats

Objectives The purpose of this study was to find out whether nasal application of buspirone could increase its bioavailability and directly transport the drug from nose to brain. Methods A nasal formulation (Bus‐chitosan) was prepared by dissolving 15.5 mg buspirone hydrochloride, 1% w/v chitosan hydrochloride and 5% w/v hydroxypropyl β‐cyclodextrin (HP‐β‐CD) in 5 ml of 0.5% sodium chloride solution. The formulation was nasally administered to rats and the plasma and brain concentration compared with that for buspirone hydrochloride solution after intravenous and intranasal (Bus‐plain) administration. The brain drug uptake was also confirmed by gamma scintigraphic study. Key findings The nasal Bus‐chitosan formulation improved the absolute bioavailability to 61% and the plasma concentration peaked at 30 min whereas the peak for nasal Bus‐plain formulation was 60 min. The AUC_0‐480 in brain after nasal administration of Bus‐chitosan formulation was 2.5 times that obtained by intravenous administration (711 ± 252 ng/g vs 282 ± 110 ng/g); this was also considerably higher than that obtained with the intranasal Bus‐plain formulation (354 ± 80 ng/g). The high percentage of direct drug transport to the brain (75.77%) and high drug targeting index (>1) confirmed the direct nose to brain transport of buspirone following nasal administration of Bus‐chitosan formulation. Conclusions These results conclusively demonstrate increased access of buspirone to the blood and brain from intranasal solution formulated with chitosan and HP‐β‐CD.