Spectrophotometric Determination of Trimethylamine-nitrogen in Cadaver Tissues for the Estimation of Late Postmortem Interval：A Pilot Study

To study the relationship between the late postmortem interval (PMI) and trimethyl-amine-nitrogen (TMA-N) in postmortem tissues of cadaver, TMA-N in muscles, livers and kidneys of rats was measured at different postmortem intervals (PMI) by using a modified spectrophotometric method. The results indicated that the detection sensitivity of TMA-N was 1 mg/L, and there was a good linear correlation between the value of absorbance (A value) and TMA-N at the concentration of 1-10 mg/L (R2=0.9991). Although TMA variation in muscles was different from that in inner organs during the time since death, TMA-N changes in cadaver tissues was positively correlated with PMI. During 2 to 7d since death, the best correlation between PMI and TMA-N concentration was found in muscles. With PMI as an independent variable, the cubic polynomial regression equation was y=-0.457x3 6.519x2-24.574x 27.207 (R2=0.969). During 3 to 8 days since death, PMI was best correlated with TMA-N concentration in inner organs. With PMI as the independent variable, the cubic polynomial regression equation was y=0.509x3-9.153x2 55.727x-95.819 (R2=0.953). It was concluded that TMA-N in tissues could be used as a new estimator for late PMI. The method used in this study offered advantages such as accuracy, sensitivity, little samples required and wide PMI estimation.     

Bioluminescent assay of microbial ATP in postmortem tissues for the estimation of postmortem interval

To study the relationship between changes of microbial ATP in four kinds of murine tis-sues and the postmortem interval （PMI）, healthy SD rats were sacrificed and their muscles, livers, spleens and kidneys were sampled at different postmortem intervals. The concentration of microbial ATP was detected using bioluminescent assay and the data was statistically analyzed. The concentra-tion of microbial ATP in muscle increased with PMI time. The peak appeared at the 7th day after death, and at the 10th day, microbial ATP in muscle tissue increased again. In internal organs, the peaks of microbial ATP were observed at the 8th day after death and the level decreased during 8–10 d. The differences in microbial ATP concentration in liver, spleen and kidney were not statistically significant. During day 0 to day 9 after death, the correlation was best between PMI and microbial ATP in muscle. With PMI as the independent variable, the cubic polynomial regression equation was Y=0.02X3–0.166X2–0.666X＋13.412 （R2=0.989, P〈0.01）. In internal organs, the best correlation was found between PMI and microbial ATP during day 0 to day 10. With PMI as the independent variable, the cubic polynomial regression equation was Y=0.016X3–0.127X2–0.809X＋13.324 （R2=0.986, P〈0.01）. There existed high correlations between PMI and microbial ATP concentration in rat tissues. Since only a small amount of tissue was needed for the detection and the sample was not affected by self-decomposition, the method may extend the time range of PMI estimation.     

Different Effects of Capsaicin on IA and IK in Pain-conduct Neurons of Rats

Capsaicin,themajoringredientinchilipep persandresponsibleforitspungenttaste,isaspe cificactivatorofnociceptoronpain conductneu rons[1].Nowcapsaicinanditsanaloguehavebeenusedinclinicasanewanalgesic[1,2].Themechanismofcapsaicinonpain conductneuronshasn'tbeenunderstoodclearlynow.Theearlierworkofourlaboratorydiscoveredthatcap saicincouldsignificantlyinhibittheactionpoten tials(APs)andthevoltage gatedsodiumchannels(VGSCs)inpain conductneuronsatlowconcen tration(1μmol/L)[3].Thepurposeofthisstudy…     

Effects of Phorbol-12,13-dibuterate on Sodium Currents and Potassium Currents in Rat Trigeminal Ganglion Neurons

The effects of phorbol-12,13-dibuterate (PDBu) on total sodium current (INa-total), tet-rodotoxin-resistant sodium current (INa-TTXr), 4-AP-sensitive potassium current (IA) and TEA-sensitive potassium current (IK) in trigeminal ganglion (TG) neurons were investigated. Whole-cell patch clamp techniques were used to record ion currents in cultured TG neurons of rats. Results revealed that 0.5 μmol/L PDBu reduced the amplitude of INa-total by (38.3±4.5)% (n=6, P<0.05), but neither the G-V curve (control: V0.5 =-17.1±4.3 mV, k=7.4±1.3; PDBu: V0.5=-15.9±5.9 mV, k=5.9±1.4; n=6, P>0.05) nor the inactivation rate constant (control: 3.6±0.9 ms; PDBu: 3.6±0.8 ms; n=6, P>0.05) was altered. 0.5 μmol/L PDBu could significantly increase the amplitude of INa-TTXr by (37.2± 3.2)% (n=9, P<0.05) without affecting the G-V curve (control: V0.5=-14.7±6.0 mV, k=6.9± 1.4; PDBu: V0.5=-11.1±5.3 mV, k=8.1±1.5; n=5, P>0.05) or the inactivation rate constant (control: 4.6±0.6 ms; PDBu: 4.2±0.5 ms; n=5, P>0.05). 0.5 μmol/L PDBu inhibited IK by (15.6±5.0) % (n=16, P<0.05), and V0.5 was significantly altered from - 4.7±1.4 mV to -7.9 ±1.8 mV (n=16, P<0.05). IA was not significantly affected by PDBu, 0.5 μmol/L PDBu decreased IA by only (0.3±3.2)% (n=5, P>0.05). It was concluded that PDBu inhibited INa-total but enhanced INa-TTXr, and inhibited IK without affecting IA. These data suggested that the activation of PKC pathway could exert the actions.     

临床医学专业毕业生综合能力评价及影响因素研究

目的 调查西安某医学院校临床医学专业毕业生的综合能力及影响因素，为完善临床医学专业学生培养模式、提高其综合能力提供科学依据。方法 以《中国本科医学教育标准——临床医学专业（2016版）》为参考，自行设计含有4个维度62个条目的《临床医学专业毕业生综合能力评价问卷》；采用随机抽样的方法以西安某医学院校临床医学专业毕业生为研究对象，对其综合能力现状进行调查；并采用SPSS 22.0统计软件包分析数据，利用多元线性回归法分析其影响因素。结果 临床医学专业毕业生临床能力领域得分最高（3.05±0.84），其次为职业素养领域（2.48±0.81），得分最低的是科学与学术领域（1.89±0.68）。各因子得分中排在前3名的依次是临床执业能力（3.39±0.76）、理论知识掌握情况（3.55±0.48）和医学知识掌握情况（2.98±0.81），得分最低的3个因子依次是文献检索能力（1.31±0.64）、全球健康问题（1.49±0.82）和自我提升意愿及能力（1.81±0.73）。利用多元逐步回归法分析综合能力影响因素，得出最优方程：Y=8.412+0.063X₆+0.190X₈+0.266X₁₀+0.031X₁₁+0.187X₁₂（X₆为工作单位层次，X₈为学习成绩排名，X₁₀为实践教学满意度，X₁₁为教学模式满意度，X₁₂为毕业后再教育满意度）。其中实践教学满意度、毕业后再教育满意度和教学模式满意度越高，学生成绩排名越高，临床毕业生的综合能力得分越高。就业层次在综合医院的毕业生，其综合能力得分要高于社区/乡镇医院等基层医院的毕业生。结论 临床医学专业学生在培养的过程中应提高实践教学质量、完善教学模式，加大科学与学术领域的培养，提高基层医疗机构再教育投入力度，提高毕业生再教育满意度，从而提高临床医学专业毕业生综合能力。     

Effect of Interleukin-1β on IA and IK Currents in Cultured Murine Trigeminal Ganglion Neurons

To investigate the effect of interleukin-1β (IL-1β) on IA and IK currents in cultured murine trigeminal ganglion (TG) neurons, whole-cell patch clamp technique was used to record the IA and IK currents before and after 20 ng/mL IL-1β perfusion. Our results showed that 20 ng/mL IL-1β inhibited IA currents (18.3±10.7)% (n=6, P<0.05). IL-1β at 20 ng/mL had no effect on G-V curve of IA but moved the H-infinity curve V0.5 from -36.6±6.1 mV to -42.4±5.2 mV (n=5, P<0.01). However, 20 ng/mL IL-1β had effect on neither the amplitude nor the G-V curve of IK. IL-1β was found to selec- tively inhibit IA current in TG neurons and the effect may contribute to hyperalgesia under various in- flammatory conditions.     

Use of rats mesenchymal stem cells modified with mHCN2 gene to create biologic pacemakers

The possibility of rats mesenchymal stem cells (MSCs) modified with murine hyperpolarization-activated cyclic nucleotide-gated 2 (mHCN2) gene as biological pacemakers in vitro was studied. The cultured MSCs were transfected with pIRES2-EGFP plasmid carrying enhanced green fluorescent protein (EGFP) gene and mHCN2 gene. The identification using restriction enzyme and sequencing indicated that the mHCN2 gene was inserted to the pIRES2-EGFP. Green fluorescence could be seen in MSCs after transfection for 24-48...     

Different suppressive effect of lidocaine on persistent Na^＋ current and transient Na^＋ current in dorsal root ganglion neurons

Objective ：To investigate the different suppressive effect of lidocaine on persistent Na^＋ current and transient Na^＋ current in injured or uninjured dorsal root ganglion neurons. Methods： Totally 23 SD rats were randomly divided into 2 groups： control group （n： 10） and chronically compressed DRG （dorsal root ganglion） group （CCD group, n= 13）. Rats were anesthetized and DRG was isolated. Single DRG neuron was isolated by enzymatic disassociation method. Persistent Na^＋ current （INap） and transient Na^＋ current （INaT） were elicited in voltage clamp mode. Results： The presence of INap was testified in most DRG neurons （38/46 neurons in CCD group and 31/39 neurons in control group, P〉0. 05）. However, the cur- rent density of INap in CCD group （4. 6±0. 6 pA/pF, n=38 neurons） was greater than that in control group （2.5±0.4 pA/pF, n=31 neurons） （P〈0. 05）. The characteristics of INap was observed and found that INap could he blocked by 0.2 μmol/L tetrodotoxin easily. Furthermore, the does-effect relationship of lidocaine on INaP and IN.T were also examined. INaP and IN.T were suppressed by different concentrations of li- docaine, the range for INap was 5-20 μmol/L and for INaT was 0. 05-2 mmol/L. Conclusion： INap and INaT were suppressed by different concentrations of lidocaine. INap was suppressed by very low concentration of lidocaine （5-20 μmol/L）. However, INaT could only be blocked by high concentration of lidocaine （0.05-2 mmol/L）.     

Effect of Tiotropium Bromide on Expression of CD_8~＋CD_（25）~＋FoxP_3~＋ Regulatory T Cells in Patients with Stable Chronic Obstructive Pulmonary Disease

The expression of CD8+CD25+FoxP3+ regulatory T cells(CD8+Tregs) in the peripheral blood of patients with stable chronic obstructive pulmonary disease(COPD),and the effect of muscarinic cholinergic receptor antagonist tiotropium bromide on the expression of CD8+Tregs were investigated.Twenty-three patients with moderate to severe stable COPD were enrolled in this study.All patients inhaled tiotropium bromide(18 μg daily) for 3 months.Before and after inhalation of tiotropium bromide,peripheral blood samples were collected from the patients,and T cells were labeled by three-color labeled monoclonal antibodies.Flow cytometry was used to detect the quantity and percentage of CD8+T cells,CD8+CD25+T cells,CD8+Tregs,CD4+T cells,CD4+CD25+T cells and CD4+CD25+FoxP3+ regulatory T cells(CD4+Tregs) respectively.The percentage of CD4+T cells was increased from(27.82±2.18)% to(35.53±1.3)%(t=3.20,P=0.004) in the peripheral blood of patients with stable COPD after inhalation of tiotropium bromide for 3 months,that of CD4+CD25+T cells was decreased from(10.03 ±1.42)% to(4.21 ±0.65)%(t=3.78,P=0.001),and that of CD8+Tregs was increased from(8.41 ±1.68)% to(21.34 ±4.20)%(t=2.72,P=0.013).At baseline,CD8+T cells,CD8+CD25+T cells and CD4+Tregs were detectable in the peripheral blood,but no significant changes were observed after treatment.Linear correlation analysis revealed that the difference before and after treatment in CD4+T cells and CD4+CD25+T cells was negatively correlated with the ratio of change in CD8+Tregs before and after treatment(r=-0.61,P=0.013;r=-0.72,P=0.001 respectively).In the peripheral blood of patients with stable COPD,there was the expression of CD8+Tregs and CD4+Tregs.Muscarinic receptor antagonist,tiotropium bromide,can promote the amplification of CD4+T cells,inhibit the expression of CD25+T cells,and enhance the expression of CD8+Tregs.CD8+Tregs and CD4+Tregs can be used as new indicators to understand the immune status of patients.They are helpful in judging the treatment efficacy and disease immunophenotype.     

阿奇霉素泡囊体外释放与体内吸收的相关性

目的 评价阿奇霉素泡囊的体外释放和体内吸收之间的相关性。方法 采用激光粒度仪测定阿奇霉素泡囊的粒径和zeta电位。建立UV法进行体外分析测定其体外释放度,高效液相色谱法进行体内分析测定大鼠口服后的血药浓度,然后分别以Loo-Riegelman法和反卷积分法计算体内吸收分数Fa和输入函数R。结果 阿奇霉素泡囊的粒径为（907.4±0.10）nm,zeta电位为（14.6 ± 0.02）mV。其体内阿奇霉素与内标峰面积之比（A）和阿奇霉素浓度（C）标准曲线回归方程为：A= 19.26C-52.69,r=0.999 0（n=3）;体外482 nm波长处光密度（D）与浓度（C）标准曲线回归方程为：D=0.014 4C-0.070 1,r=0.999 6（n=3）,回收率均符合要求。以体外累计释放度Y与Fa和R建立的回归方程分别为：Fa=0.981 8Y + 1.083 1,r=0.956 5、R=0.763 5Y-15.699,r=0.862 7。结论 阿奇霉素泡囊体外释放与体内吸收之间没有相关性。     

Prediction of Trend between Water Environment Pollution of D Lake and Death Rate of Malignancy in Population

Waterisoneofthemostnecessarybasicsforhu manlifeandproductionactivities .Alotofattentionhasbeenpaidto predictionbetweenwaterenviron mentpollutionandpopulationhealth[1- 3] .Thee cosystemwherehumanexistsisverycomplexandthemechanismsbywhichwatercontaminationaffectpopulationhealtharealsoverycomplicated .Re searcheshaveshownthatbladdercancer ,stomachcancer ,coloncancer ,rectumcancer ,esophaguscan cerandlivercancerareamongthecommoncancerswhichhaveshownstatisticalsignificancebetweenpopulationandwatero…     

Sex Difference in the Repolarization Currents of Rabbit Ventricular Cells

Female gender is associated with an increasedrisk of drug-associated torsade de pointes (TdP) .Many kinds of drugs such as class ⅠAand class Ⅲantiarrhythmia , some antibiotics , antidepressantdrugs have the potential of inducing TdP. It isthought that the slower repolarization of femaleheart accounts for the higher incidence of TdP.However ,the current difference between male andfemale is poorly known. Our previous experi menthas shown that rabbits presented the same differ-ence of TdP a…     

谷氨酸对人交感神经母细胞瘤SH-SY5Y细胞系超极化激活的阳离子通道的影响

目的 观察谷氨酸(Glu)对交感神经细胞超极化激活的阳离子通道(I_h通道)活动的影响。 方法 采用人交感神经母细胞瘤SH-SY5Y细胞系作为交感神经细胞模型,用全细胞电压箝方式记录I_h通道电流。 结果 SH-SY5Y细胞存在I_h通道电流;Glu(1mmol/L)可抑制SH-SY5Y细胞I_h电流的K⁺电流成分,但增强I_h电流的Ca²⁺电流和Na⁺电流成分,综合效应是使I_h电流增大。 结论 Glu可增大SH-SY5Y细胞的I_h电流。这一效应提示,Glu可能通过诱发交感神经元去极化并促进其传出冲动增加。     

K<Superscript>+</Superscript> channels and their effects on membrane potential in rat bronchial smooth muscle cells

Summary In order to investigate the K⁺ channels and their effects on resting membrane potential (Em) and excitability in rat bronchial smooth muscle cells (BSMCs), the components of outward K⁺ channel currents and the effects of K⁺ channels on Em and tension in rat bronchial smooth muscle were observed by using standard whole-cell recording of patch clamp and isometric tension recording techniques. The results showed that under resting conditions, total outward K⁺ channel currents in freshly isolated BSMCs were unaffected by ATP-sensitive K⁺ channel blocker. There were two types of K⁺ currents: voltage-dependent delayed rectifier K⁺ channel (K_v) and large conductance calcium-activated K⁺ channel (BK_Ca) currents. 1 mmol/L 4-aminopyridine (4-AP, an, inhibitor of K_V) caused a significant depolarization (from −8.7±5.9 mV to −25.4±3.1 mV,n=18,P<0.001). In contrast, 1 mmol/L tetraethylammonium (TEA, an inhibitor of BK_Ca) had no significant effect on Em (from −37.6±4.8 mV to −36.8±4.1 mV,n=12,P>0.05). 4-AP caused a concentration-dependent contraction in resting bronchial strips. TEA had no effect on resting tension, but application of 5 mmol/L TEA resulted in a left shift with bigger pD₂ (the negative logarithm of the drug concentration causing 50% of maximal effect) (from 6.27±0.38 to 6.89±0.54,n=10,P<0.05) in the concentration-effect curve of endothine-1, and a right shift with smaller pD₂ (from 8.10±0.23 to 7.69±0.08,n=10,P<0.05) in the concentration-effect curve of isoprenaline. It was suggested that in rat BSMCs there may be two types of K⁺ channels, K_v and BK_Ca, which serve distinct roles. K_v participates in the control of resting Em and tension. BK_Ca is involved in the regulation of relaxation or contraction associated with excitation. LIU Xiansheng, male, born in 1969, M. D., Ph. D. This project was supported by a grant from the National Natural Sciences Foundation of China (No. 30270583).     

沈阳地区健康成人脉冲振荡肺功能正常值分析

 目的探讨沈阳地区健康成人脉冲振荡肺功能正常参考值及预计值。方法对100 例（男59 例,女41 例）常规肺功能
正常的健康成人进行脉冲振荡肺功能测定,求出脉冲振荡技术（IOS）各参数［呼吸总阻抗（Zrs）、总呼吸阻力（R5）、中心气道阻力
（R₂₀）、周边弹性阻力（X5）等］参考值范围并建立多元回归方程。结果男性预计值公式：Zrs=10.188-4.434*lgH;X₅=-0.068-
1.009*10-5*A2;R₅=8.675-3.62*lgH-0.435*lgA;R₂₀=1.768-1.345*10-5*H2-5.098*10-8*eA。女性预计值公式：Zrs=10.081+1.564*10-33*eA-
4.388*lgH;X₅=-0.287-6.559*10-34*eA+6.994*10-6H2;R₅=9.745-4.241*lgH;R₂₀=0.961-2.408*10-5*H2。结论沈阳地区健康成人脉
冲振荡各参数参考值范围及预计值公式与国内、外有差异。建议各地区建立适合本地区自己的预计值公式。     

Effect of Cigarette Smoke Extract on the Role of Protein Kinase C in the Proliferation of Passively Sensitized Human Airway Smooth Muscle Cells

Cigarette smoke(CS) is ani mportant risk fac-tor involvedin the development and progression ofasthma[1]. Ovalbumin ( Ova) sensitization inducesairway hyperresponsiveness ( AHR) to inhaled CSin guinea pigs[2]. Airway smooth muscle prolifera-tion plays an i mportant role in airway remodelingin asthma . Protein kinase C (PKC) is one of thecrucial kinases in the intracellular signal transduc-tion pathway .CSEcanincrease PKC's activationinhuman bronchial epithelial cells[3].Because airwaysm…     

Association of polymorphisms in angiotensin II receptor genes with aldosterone-producing adenoma

This study examined the association of polymorphisms in angiotensinⅡreceptor genes(AT1R and AT2R) with the risk for aldosterone-producing adenoma(APA) in a Chinese Han population.Four polymorphisms including rs5182(573T/C) in exon 4,rs5186(1166A/C) in 3’-untranslated region(3’-UTR) in AT1R gene and rs5194(2274G/A) in 3’-UTR,rs1403543(1675G/A) in intron 1 in AT2R gene were detected in 148 APA patients and 192 normal subjects(serving as control) by using a MGB-Taqman probe.The distribution of genotypes of each locus was in accordance with Hardy-Weinberg Equilibrium(HWE) in the APA and control groups(P>0.05).The allele A frequency at rs5194 was significantly higher in the APA group(0.49) than in the control group(0.35)(χ2=12.08,P=0.001).Subjects with homozygotic genotype AA and heterozygotic genotype GA were at an increased risk for APA as compared to those with GG genotype(OR=2.66,95% CI=1.45-4.87;OR=1.67,95% CI=1.02-2.74).Furthermore,rs5194 single-nucleotide polymorphism(SNP) at AT2R gene was significantly associated with APA in additive(OR=1.64,95% CI=1.21-2.20,P=0.001),dominant(OR=1.94,95% CI=1.23-3.06,P=0.003),and recessive model(OR=2.01,95% CI=1.17-3.45,P=0.01).It was concluded that rs5194 polymorphism at AT2R gene was associated with the risk for APA,which may constitute a genetic marker of APA.     

溴吡斯的明磷脂复合物纳米乳体外溶出度与体内吸收的相关性

目的 采用Loo-Riegelman法评价溴吡斯的明磷脂复合物纳米乳(PPNE)体内外的相关性.方法 制备PPNE后,采用动态膜透析法研究PPNE体外释放行为,高效液相色谱法(HPLC)测定大鼠口服制剂后的血药浓度,以Loo-Riegelman法计算体内吸收百分数(Fa),并与体外累积释放率作线性回归.结果 PPNE的体外累积释放率(X)与体内Fa(Y)建立的线性方程为Y=1.376 9X-47.543 2,r=0.941 1,r大于相关系数临界值r(6.0.001) (P＜0.001).结论 PPNE体外释放与体内吸收之间具有良好的相关性.     

高效液相色谱法测定草酸钙结石大鼠尿中草酸含量

目的 建立高效液相色谱法(HPLC)检测大鼠尿液中草酸含量。方法 将SPF级雄性健康Wistar大鼠24只采用随机数字表法分为空白对照组(n=12)和乙二醇组(n=12)。空白对照组给予去离子水喂养,每天以1 ml生理盐水灌胃;乙二醇组给予1%乙二醇自由饮水喂养,每天2%氯化铵2 ml灌胃。造模28 d后收集两组大鼠24 h尿液,采用HPLC法测定尿中草酸含量,并与铬酸钾氧化甲基红催化光度法的结果进行比较。HPLC法采用色谱柱Aglient 5TC-C₁₈(250×4.6 mm,5 μm),以甲醇(0.1 mol/L)、醋酸铵水溶液(15∶85)为流动相,流速为1.2 ml/min,紫外检测波长为314 nm,柱温20 ℃。结果 大鼠尿液中高、低浓度草酸标准曲线分别为y=5909.1x+378730,R²=0.9984和y=7810.5x-16635,R²=0.9967;最低检测浓度为5 μg/ml,大鼠尿液中草酸高浓度线性范围为62.50~2000.00 μg/ml,低浓度线性范围为6.25~100.00 μg/ml。平均回收率为95.1%,日内及日间精密度分别为3.4%~10.8%和3.8%~9.4%。HPLC法和铬酸钾氧化甲基红催化光度法均显示乙二醇组大鼠尿草酸浓度和24 h尿草酸含量显著高于空白对照组[尿草酸浓度:(736.35±254.52)μg/ml比(51.56±36.34)μg/ml,(687.35±234.53)μg/ml比(50.24±42.34)μg/ml;24 h尿草酸含量:(11.23±4.12)mg比(0.87±0.45)mg,(9.89±3.55)mg比(0.77±0.65)mg;P均＜0.01];两种方法检测出的尿草酸浓度和24 h尿草酸含量差异无统计学意义(P均＞0.05)。结论 HPLC法简单快速、回收率高、精密度好,与铬酸钾氧化甲基红催化光度法检测结果一致,适用于大鼠尿中草酸含量的测定。     

Differential effects ofd, l-Sotalol andd-Sotalol on isoproterenol-increased delayed rectifier outward potassium current in guinea pig single ventricular myocytes

Summary The aim of this study was to compare the effects ofd, l-Sotalol andd-Sotalol on the delayed rectifier K⁺ outward current in the presence of isoproterenol at different concentrations. Time-dependent delayed rectifier K⁺ outward currents were measured in isolated guinea pig single myocytes using the whole-cell configuration of the patch-clamp technique. Currents were measured in response to 300 ms depolarizing pulses from a holding potential of −40 mV in three experimental protocols [control, isoproterenol (10^-9mollL-10^-6 mollL), and isoproterenol (10^-9mollL-10^-6mollL) plus eitherd, l-Sotalol (10^-4 mollL) ord-Sotalol (10^-4 mollL)]. I_k tail currents were measured upon repolarization to −40 mV. It was found that Ik was significantly amplified in the presence of isoproterenol (10^-9 mollL-10^-6 mollL) plusd-Sotalol. At 10^-8 mollL isoproterenol, I_k was increased by 92. 7%± 17. 1% (P<0. 05) and 54. 3 %±13. 4% afterd-Sotalol addition (P<0. 05). In contrast,d, l-Sotalol completely conteracted the increase of I_k by isoproterenol (<10^-8 mollL), and compared to control, Ik was decreased by 35. 6%± 8. 1 % at 10^-8 mollL isoproterenol plusd, l-Sotalol (P<0. 05). It is concluded that the β-adrenergic blocking property ofd, l-Sotalol but not that ofd-Sotalol maintains the delayed rectifier K⁺ outward current blockade in the presence of isoproterenol in guinea pig myocytes. This might contribute to a superior antiarrhythmic efficacy as compared tod-Sotalol.