肺动脉平滑肌细胞氧敏感钾通道与低氧性肺血管收缩

Lopez Barnc于1988年采用全细胞膜片钳技术发现了大鼠颈动脉体Ⅰ型细胞膜上对低氧敏感的钾（K^＋）通道,称为“氧敏感K^＋通道”（O2-sensitive K^＋ channels）。在肺动脉平滑肌细胞（PASMCs）巾亦存在此种离子通道。低氧时PASMCs的K^＋外向电流发生抑制,膜发生除极化,继而L^-型电压门控Ca^2＋通道开放,     

Normal urinary calcium/creatinine ratios in African-American and Caucasian children

A random urine calcium/creatinine ratio (UCa/Cr) is of practical use in screening for hypercalciuria. However, due to worldwide variations, reference values for the pediatric population are not yet well established. Furthermore, no study has been conducted to establish normal UCa/Cr values in young African-American (AA) children. It has also been previously reported that an elevated UCa/Cr is related to a high urine Na/K ratio (UNa/K). The objectives of the present study were: (1) to set normal values of random UCa/Cr by age and race in the pediatric population of Metropolitan Kansas City, (2) to identify potential racial differences in UCa/Cr between Caucasian (CS) and AA children, and (3) to determine the relationship between UCa/Cr and UNa/K in healthy children.A total of 368 healthy children of both genders were enrolled in the study. They were divided into four age groups as follows: (1) <7 months, (2) 8–18 months, (3) 19 months to 6 years, and (4) 7–16 years. Each group was subdivided into AA and CS. A non-fasting random urine specimen from each subject was analyzed for Ca, Na, K and creatinine.The median UCa/Cr values for AA were: (1) 0.13, (2) 0.09, (3) 0.06, and (4) 0.04 and for CS they were (1) 0.26, (2) 0.11, (3) 0.10, and (4) 0.09. The data showed a strong inverse relationship between UCa/Cr and age, the youngest children demonstrating the highest UCa/Cr. In each age group, UCa/Cr in CS exceeded the corresponding value in AA. The age-dependent 95th percentiles of UCa/Cr values for CS were (1) 0.70, (2) 0.50, (3) 0.28, and (4) 0.20 and for AA they were (1) 0.38 and (3) 0.24. Due to outliers, the 95th percentile could not be established for the other two AA subgroups. The relationship between UCa/Cr and UNa/K was found to be extremely weak in both AA (r ² =0.00005) and CS (r ² =0.02). On the other hand, a strong linear correlation was observed between UNa/K and age (CS r ² =0.23, P<0.001, AA r ² =0.19, P<0.001), explaining in part the lack of correlation between UNa/K and UCa/Cr.We conclude that the child’s age, ethnicity and geographic location should be taken into consideration when assessing UCa/Cr ratio. Contrary to what has previously been reported in hypercalciuric children, no significant relationship was found between UCa/Cr and UNa/K in healthy children. Received: 7 June 2000 / Revised: 21 September 2000 / Accepted: 23 September 2000     

氯胺酮对离体大鼠心室肌细胞瞬时外向钾电流的影响

目的研究氯胺酮对大鼠心室肌细胞瞬时外向钾电流(Ito)的影响。方法酶解法分离大鼠心室肌细胞,采用全细胞膜片钳技术记录Ito,观察50μmol/L氯胺酮对Ito电流-电压曲线以及不同浓度氯胺酮对Ito的影响,并研究氯胺酮对Ito通道动力学的影响。结果钳制电压-40mV,刺激电压 70mV条件下,临床相关浓度的氯胺酮50μmol/L使Ito的电流峰值降低23·4%(P<0·01),冲洗后,Ito能够完全恢复。5、10、50、100、500、1000、5000μmol/L的氯胺酮抑制Ito呈浓度依赖性,电流抑制率分别为(13·8±9·7)%、(17·5±6·7)%、(23·4±8·8)%、(31·5±6·7)%、(63·3±5·5)%、(79·7±2·7)%、(88·9±4·4)%,其半数有效浓度(IC50)为299μmol/L。100μmol/L的氯胺酮对激活曲线没有影响;使Ito的失活曲线明显右移,半数失活电压(V1/2)在给药前后数值分别为(-28·27±0·20)mV和(-25·34±0·27)mV(P<0·01),斜率因子(k)值分别为(3·23±0·46)mV和(3·40±0·55)mV(P>0·05)。结论氯胺酮可明显阻滞大鼠心室肌的Ito,这是氯胺酮延长大鼠心室肌动作电位的机理之一,同时氯胺酮使Ito的失活曲线右移。     

2型糖尿病大鼠肠系膜动脉平滑肌细胞大电导钙激活钾通道α、β1亚基蛋白及mRNA表达水平变化

目的  探讨2型糖尿病（T2DM）大鼠肠系膜动脉平滑肌细胞大电导钙激活钾通道（BKCa）α、β1亚基蛋白及mRNA表达水平变化,从分子水平阐明T2DM大鼠肠系膜动脉平滑肌细胞膜BKCa通道活性改变的具体机制,为T2DM的综合治疗提供新靶点;为特异性针对此环节的药物研发提供实验依据。方法  SD大鼠高糖高脂饮食1个月后腹腔注射链脲菌素STZ（25 mg/kg）建立T2DM大鼠模型。免疫印记法和实时定量聚合酶链式反应测定肠系膜动脉BKCa通道α和β1亚基的蛋白和mRNA表达水平。结果  ①免疫印迹结果显示：模型组在第8周和第12周肠系膜动脉大电导钙激活钾通道（BKCa）α蛋白相对表达量分别为（1.093±0.251）和（0.921±0.153）,与对照组比较差异无统计学意义（P >0.05）;β1蛋白相对表达量分别为（0.334±0.200）和（0.193±0.310）,与对照组比较差异有统计学意义（P <0.05）。②实时定量聚合酶链式反应结果显示,模型组在第8周和第12周肠系膜动脉BKCa α亚基mRNA的表达分别为（1.15±0.03）和（0.92±0.04）,与对照组比较差异无统计学意义（P >0.05）;β1亚基mRNA的表达分别为（0.47±0.10）和（0.37±0.12）,与对照组比较差异有统计学意义（P <0.05）。结论  T2DM大鼠肠系膜动脉BKCa β1亚基蛋白和mRNA表达在8周及12周明显降低。

     

Age-Related Changes in Cochlear Endolymphatic Potassium and Potential in CD-1 and CBA/CaJ Mice

The CD-1 mouse strain is known to have early onset of hearing loss that is progressive with aging. We sought to determine whether a disturbance of K⁺ homeostasis and pathological changes in the cochlear lateral wall were involved in the age-related hearing loss (AHL) of CD-1 as compared to the CBA/CaJ strain which has minimal AHL. In the present study, the endocochlear potential (EP) and endolymphatic K⁺ concentration ([K⁺]_e) were measured in both strains of mice with double-barrel microelectrodes at young (1–2 mo) and old (5–9 mo) ages. CBA/CaJ mice displayed no changes with aging in EP and [K⁺]_e of the basal turn. In the apical turn, there was a small positive shift of the EP (10 mV) with aging under both normoxic and acute anoxic conditions (–EP), without any change of [K⁺]_e. Further, there were no obvious pathological changes in the lateral wall of CBA/CaJ mice. By contrast, old CD-1 mice displayed a significantly reduced [K⁺]_e by 30% in both basal and apical turns with no significant changes in normoxic EP. The –EP in the apical turn was significantly reduced in magnitude by 6 mV. A severe loss of cells with aging was observed in the region of type IV fibrocytes of the apical and basal turns and of type II fibrocytes in the basal turn. A complete degeneration of organ of Corti was also observed at the basal turn of old CD-1 mice, as well as a basalward decline of spiral ganglion neuron density. The pathological changes in spiral ligament of CD-1 mice were similar to those of an inbred mouse strain C57BL/6J that expresses an AHL gene (ahl) and might be a primary etiology of AHL of CD-1 mice. These findings have ramifications for our understanding of AHL and for interpretation of genetic mutations in a CD-1 background.     

枸橼酸铋钾的分子组成研究

目的：考察枸橼酸铋钾的分子组成。方法：采用容量法测定铋含量,原子吸收法测定钾的含量,离子色谱法测定枸橼酸根的含量,核磁共振氢谱进行结构推测;采用X-衍射试验和电子显微镜扫描法对晶型结构进行初步研究;加速稳定性试验考察3个分子组成部分在试验前后百分含量之比的变化。结果：以干燥品计,本品3个分子组成部分的百分含量分别为：铋35%-38%,钾7%-11%,枸橼酸根49%-52%,核磁图谱和数据显示本品有3种同分异构体,分子结构组成可能为铋∶钾∶枸橼酸=2∶2∶2;X-衍射试验和电镜扫描结果表明本品可能存在无定形、单晶和多晶3种形态;3个结构组成部分在加速试验前后的百分含量之比基本一致。结论：枸橼酸铋钾的3个结构组成部分的百分含量在一定范围内,可能存在3种不同的晶型形态,本品结构组成较稳定。     

High frequency of contact allergy to gold sodium thiosulfate

When gold sodium thiosulfate was added to the patch test standard series, positive reactions were obtained in 8.6% of 823 consecutive patients with suspect contact allergy. The test reactions were clinically of an allergic type and, in several cases, long-lasting. There was no correlation with other allergens in the standard series. In a special study on 38 patients with contact allergy to gold sodium thiosulfate, the following principal findings were obtained: positive patch tests to the compound itself in dilute concentration; positive patch tests to potassium dicyanoaurate; negative patch tests to gold sodium thiomalate, sodium thiosulfate, and metallic gold; positive intradermal tests to gold sodium thiomalate. Our findings make gold sodium thiosulfate the 2nd most common contact allergen after nickel sulfate. It is suggested that a positive skin test to gold sodium thiosulfate represents gold allergy.     

Heterogeneous of potassium currents in free wall myocytes from the infarcted rabbit ventricle and regression effects of imidapril

Objective To define the heterogeneous changes of ion channels in the noninfarcted myocardium after myocardial infarction in rabbit and effects of imidapril.Mehods Rabbits with left coronary artery ligation were prepared and allowed to recover for 8 wk.Myocytes were isolated from subendocardial,midmyocardial and subepicardial regions of the noninfarcted left ventricular free wall.Ion currents were recorded with whole-cell patch clamp way.Results The densities of the transient outward K+ currents (I to) and the inward rectifier K+ currents (I K1) were greatly reduced in midmyocardium and subepicardium while two currents reduced gently in subendocardium.The densities of the delayed rectifier K+ currents (I K) were reduced in noninfarcted three layers similarly.Imidapril could reverse the changes of membrane currents in healed myocardial infarction cells and depress the dispersion of repolarization.Conclusions The heterogeneities of K currents are enhanced in noninfarcted area.Normalization of heterogeneous changes of repolarization after treatment with imidapril was observed.