Objective Large-conductance calcium-activated potassium(BKCa)channel modulates vascular smooth muscle tone.In the present study,we tested the hypothesis that salt,one of the factors which significantly influence blood...Objective Large-conductance calcium-activated potassium(BKCa)channel modulates vascular smooth muscle tone.In the present study,we tested the hypothesis that salt,one of the factors which significantly influence blood pressure(BP),can regulate BKCa activity and then elevate blood pressure.Methods Male Sprague-Dawley rats aged 6 weeks were randomized into high salt diet group(HS)and control group,fed with high salt diet(containing 5% NaCl)and standard rat chow(containing 0.4% NaCl)respectively for 16 weeks.Tail systolic blood pressure(SBP),body weight(BW)and 24-hour urinary output were tested every 4 weeks.Content of urinary Na+ was detected using flame spectrophotometrical method.At the end of 16 weeks,all the rats were killed,the mesenteric arteries were obtained,and single mesenteric smooth muscle cells were isolated at once.The resting membrane potential(Em),the total potassium currents and the currents after perfusion with TEA solution of the cells were all recorded by whole cell patch clamp.The transcriptions of BKCa channel α and β1 subunits in mesenteric arterial vascular smooth muscle cells(VSMC)of each group were calculated by real-time RT-PCR.Results There was no difference in SBP and BW at each stage between control group and HS group;the urinary Na+ level in HS animals was elevated significantly after 4 weeks.The negative values of Em in HS group VSMCs were reduced compared with those in the control group.Transcriptions of β1 subunit of BKCa channels were decreased in HS group,but α subunit transcriptions did not differ between the two groups.Whole cell potassium currents did not differ between HS and control groups,but BKCa currents of HS group VSMCs were lower than those of control group ones.Conclusion Even without elevating SBP,salt-loading can still modulate the expression and activity of BKCa channel in the mesenteric arterial VSMC and elevate vascular tone.展开更多
Objective:To study the correlation of large conductance Ca2+ activated K+ channel (BKCa)α andβ subunit expression in uterine smooth muscle with the postpartum hemorrhage induced by uterine inertia.Methods: The puerp...Objective:To study the correlation of large conductance Ca2+ activated K+ channel (BKCa)α andβ subunit expression in uterine smooth muscle with the postpartum hemorrhage induced by uterine inertia.Methods: The puerperae who underwent cesarean section and had postpartum hemorrhage induced by uterine inertia in Panzhihua Women and Children Health Hospital between March 2015 and May 2017 were selected as the hemorrhage group of the study, and the puerperae who underwent cesarean section and were without postpartum hemorrhage in Panzhihua Women and Children Health Hospital during the same period were selected as the control group. Proper amount of uterine muscle tissue was collected during the cesarean section to measure the expression of BKCaα andβ subunits and the levels of contraction-related proteins in uterine muscle as well as the contraction characteristic parameters of the uterine muscle.Results: The mRNA expression and protein expression of BKCaα andβ subunits in uterine muscle tissue of hemorrhage group were significantly higher than those of control group;the contraction amplitude, contraction frequency and contraction activity of uterine muscle tissue as well as the OTR, COX2, CX43 and HSP27 levels in uterine muscle tissue of hemorrhage group were significantly lower than those of control group;the BKCaα andβ subunit expression in uterine muscle tissue of hemorrhage group were negatively correlated with the contraction amplitude, contraction frequency and contraction activity as well as the OTR, COX2, CX43 and HSP27 levels.Conclusion: The high expression of BKCa in uterine smooth muscle can reduce the uterine muscle contractility and decrease the levels of contraction-related proteins, and it is closely related to the occurrence of postpartum hemorrhage induced by uterine inertia.展开更多
In this study, we investigated the effects of a combination of Ginkgo biloba extracts （GBE） and phosphodiesterase type 5 （PDE-5） inhibitors on the muscular tone of the corpus cavernosum and potassium channel activ...In this study, we investigated the effects of a combination of Ginkgo biloba extracts （GBE） and phosphodiesterase type 5 （PDE-5） inhibitors on the muscular tone of the corpus cavernosum and potassium channel activity of corporal smooth muscle cells. Strips of corpus cavernosum from male New Zealand white rabbits were mounted in organ baths for isometric tension studies. After contraction with 1 × 10^-5 mol I^-1 norepinephrine, GBE （0.01-1 mg ml^-1） and mirodenafil （0.01-100 nmol I^-1） were added together into the organ bath. In electrophysiological studies, whole-cell currents were recorded by the conventional patch-clamp technique in cultured smooth muscle cells of the human corpus cavernosum. The corpus cavemosum was relaxed in response to GBE in a dose-dependent manner （from 0.64%±8.35% at 0.01 mg ml^-1 to 52.28%±11.42% at 1 mg ml^-1）. After pre-treatment with 0.03 mg ml^-1 of GBE, the relaxant effects of mirodenafil were increased at all concentrations, After tetraethylammonium （TEA） （1 mmol I^-1） administration, the increased effects were inhibited （P〈0.01）. Extracellular administration of GBE increased the whole-cell K^＋ outward currents in a dose-dependent fashion. The increase of the outward current was inhibited by I mmol 1-1 TEA. These results suggest that GBE could increase the relaxant potency of mirodenafil even at a minimally effective dose. The K＋ flow through potassium channels might be one of the mechanisms involved in this synergistic relaxation.展开更多
Direct observation was made by using the patch-clamp technique with a specially designed microperfusion system to investigate the effect of acetylcholine (Ach 10^(-6) mol/L) elicited endothelium-derived relaxing facto...Direct observation was made by using the patch-clamp technique with a specially designed microperfusion system to investigate the effect of acetylcholine (Ach 10^(-6) mol/L) elicited endothelium-derived relaxing factor (EDRF) on the calcium-activated potassium channel (IK(Ca))in the smooth muscle cells of mesenteric resistance vessels in Wistar rats. Activation of IK(Ca) was firstly observed by inducing the elicited EDRF or sodium nitroprusside (SNP 10^(-8) mol/L) under various clamping voltages in cell-attached configuration. While the pipette solution contained KCl 126 mmol/L and the bath solution contained KCl 5.9 mmol/L, two types of conductances of calcium-activated potassium current being 76.4±2.3 pS(mean±S.E. n = 7) and 160.3±7.5 pS (mean±S.E. n= 7) were recorded during the EDRF activation, one type of conductance being 100.5±2.8 pS (mean±S.E. n = 6) was activated by nitric oxide (NO) which is an effective component from SNP. Differences in kinetic characteristics of these channels between EDRF and NO activation were found, particularly the probability of the channel being open in EDRF activation was obviously greater than that in NO stimulation. It has been shown that the potassium channel mechanisms involved in the EDRF and NO actions might be different.展开更多
Background Diabetes mellitus is associated with coronary dysfunction, contributing to a 2- to 4-fold increase in the risk of coronary heart diseases. The mechanisms by which diabetes induces vasculopathy involve endot...Background Diabetes mellitus is associated with coronary dysfunction, contributing to a 2- to 4-fold increase in the risk of coronary heart diseases. The mechanisms by which diabetes induces vasculopathy involve endothelial-dependent and -independent vascular dysfunction in both type 1 and type 2 diabetes mellitus. The purpose of this study is to determine the role of vascular large conductance Ca2＋-activated K＋ （BK） channel activities in coronary dysfunction in streptozotocin-induced diabetic rats. Methods Using videomicroscopy, immunoblotting, fluorescent assay and patch clamp techniques, we investigated the coronary BK channel activities and BK channel-mediated coronary vasoreactivity in streptozotocin-induced diabetic rats. Results BK currents （defined as the iberiotoxin-sensitive K＋ component） contribute （65＋4）% of the total K＋currents in freshly isolated coronary smooth muscle cells and 〉50% of the contraction of the inner diameter of coronary arteries from normal rats. However, BK current density is remarkably reduced in coronary smooth muscle cells of streptozotocin-induced diabetic rats, leading to an increase in coronary artery tension. BK channel activity in response to free Ca2＋ iS impaired in diabetic rats. Moreover, cytoplasmic application of DHS-1 （a specific BK channel i~ subunit activator） robustly enhanced the open probability of BK channels in coronary smooth muscle cells of normal rats. In diabetic rats, the DHS-1 effect was diminished in the presence of 200 nmol/L Ca2＋ and was significantly attenuated in the presence of high free calcium concentration, i.e., 1 μmol/L Ca2＋. Immunoblotting experiments confirmed that there was a 2-fold decrease in BK-β1 protein expression in diabetic vessels, without alterinq the BK channel a-subunit expression.Although the cytosolic Ca2＋ concentration of coronary arterial smooth muscle cells was increased from （103±23） nmol/L （n=5） of control rats to （193±22） nmol/L （n=6, P 〈0.05） of STZ-induced diabetic rats, reduced BK-β1 expression made these channels less sensitive to intracellular Ca2＋, which in turn led to enhanced smooth muscle contraction. Conclusions Our results indicated that BK channels are the key determinant of coronary arterial tone. Impaired BK channel function in diabetes mellitus is associated with down-regulation of BK-β1 expression and reduction of the β1-mediated BK channel activation in diabetic vessels.展开更多
文摘Objective Large-conductance calcium-activated potassium(BKCa)channel modulates vascular smooth muscle tone.In the present study,we tested the hypothesis that salt,one of the factors which significantly influence blood pressure(BP),can regulate BKCa activity and then elevate blood pressure.Methods Male Sprague-Dawley rats aged 6 weeks were randomized into high salt diet group(HS)and control group,fed with high salt diet(containing 5% NaCl)and standard rat chow(containing 0.4% NaCl)respectively for 16 weeks.Tail systolic blood pressure(SBP),body weight(BW)and 24-hour urinary output were tested every 4 weeks.Content of urinary Na+ was detected using flame spectrophotometrical method.At the end of 16 weeks,all the rats were killed,the mesenteric arteries were obtained,and single mesenteric smooth muscle cells were isolated at once.The resting membrane potential(Em),the total potassium currents and the currents after perfusion with TEA solution of the cells were all recorded by whole cell patch clamp.The transcriptions of BKCa channel α and β1 subunits in mesenteric arterial vascular smooth muscle cells(VSMC)of each group were calculated by real-time RT-PCR.Results There was no difference in SBP and BW at each stage between control group and HS group;the urinary Na+ level in HS animals was elevated significantly after 4 weeks.The negative values of Em in HS group VSMCs were reduced compared with those in the control group.Transcriptions of β1 subunit of BKCa channels were decreased in HS group,but α subunit transcriptions did not differ between the two groups.Whole cell potassium currents did not differ between HS and control groups,but BKCa currents of HS group VSMCs were lower than those of control group ones.Conclusion Even without elevating SBP,salt-loading can still modulate the expression and activity of BKCa channel in the mesenteric arterial VSMC and elevate vascular tone.
文摘Objective:To study the correlation of large conductance Ca2+ activated K+ channel (BKCa)α andβ subunit expression in uterine smooth muscle with the postpartum hemorrhage induced by uterine inertia.Methods: The puerperae who underwent cesarean section and had postpartum hemorrhage induced by uterine inertia in Panzhihua Women and Children Health Hospital between March 2015 and May 2017 were selected as the hemorrhage group of the study, and the puerperae who underwent cesarean section and were without postpartum hemorrhage in Panzhihua Women and Children Health Hospital during the same period were selected as the control group. Proper amount of uterine muscle tissue was collected during the cesarean section to measure the expression of BKCaα andβ subunits and the levels of contraction-related proteins in uterine muscle as well as the contraction characteristic parameters of the uterine muscle.Results: The mRNA expression and protein expression of BKCaα andβ subunits in uterine muscle tissue of hemorrhage group were significantly higher than those of control group;the contraction amplitude, contraction frequency and contraction activity of uterine muscle tissue as well as the OTR, COX2, CX43 and HSP27 levels in uterine muscle tissue of hemorrhage group were significantly lower than those of control group;the BKCaα andβ subunit expression in uterine muscle tissue of hemorrhage group were negatively correlated with the contraction amplitude, contraction frequency and contraction activity as well as the OTR, COX2, CX43 and HSP27 levels.Conclusion: The high expression of BKCa in uterine smooth muscle can reduce the uterine muscle contractility and decrease the levels of contraction-related proteins, and it is closely related to the occurrence of postpartum hemorrhage induced by uterine inertia.
文摘In this study, we investigated the effects of a combination of Ginkgo biloba extracts （GBE） and phosphodiesterase type 5 （PDE-5） inhibitors on the muscular tone of the corpus cavernosum and potassium channel activity of corporal smooth muscle cells. Strips of corpus cavernosum from male New Zealand white rabbits were mounted in organ baths for isometric tension studies. After contraction with 1 × 10^-5 mol I^-1 norepinephrine, GBE （0.01-1 mg ml^-1） and mirodenafil （0.01-100 nmol I^-1） were added together into the organ bath. In electrophysiological studies, whole-cell currents were recorded by the conventional patch-clamp technique in cultured smooth muscle cells of the human corpus cavernosum. The corpus cavemosum was relaxed in response to GBE in a dose-dependent manner （from 0.64%±8.35% at 0.01 mg ml^-1 to 52.28%±11.42% at 1 mg ml^-1）. After pre-treatment with 0.03 mg ml^-1 of GBE, the relaxant effects of mirodenafil were increased at all concentrations, After tetraethylammonium （TEA） （1 mmol I^-1） administration, the increased effects were inhibited （P〈0.01）. Extracellular administration of GBE increased the whole-cell K^＋ outward currents in a dose-dependent fashion. The increase of the outward current was inhibited by I mmol 1-1 TEA. These results suggest that GBE could increase the relaxant potency of mirodenafil even at a minimally effective dose. The K＋ flow through potassium channels might be one of the mechanisms involved in this synergistic relaxation.
基金Project supported by the National Natural Science Foundation of China.
文摘Direct observation was made by using the patch-clamp technique with a specially designed microperfusion system to investigate the effect of acetylcholine (Ach 10^(-6) mol/L) elicited endothelium-derived relaxing factor (EDRF) on the calcium-activated potassium channel (IK(Ca))in the smooth muscle cells of mesenteric resistance vessels in Wistar rats. Activation of IK(Ca) was firstly observed by inducing the elicited EDRF or sodium nitroprusside (SNP 10^(-8) mol/L) under various clamping voltages in cell-attached configuration. While the pipette solution contained KCl 126 mmol/L and the bath solution contained KCl 5.9 mmol/L, two types of conductances of calcium-activated potassium current being 76.4±2.3 pS(mean±S.E. n = 7) and 160.3±7.5 pS (mean±S.E. n= 7) were recorded during the EDRF activation, one type of conductance being 100.5±2.8 pS (mean±S.E. n = 6) was activated by nitric oxide (NO) which is an effective component from SNP. Differences in kinetic characteristics of these channels between EDRF and NO activation were found, particularly the probability of the channel being open in EDRF activation was obviously greater than that in NO stimulation. It has been shown that the potassium channel mechanisms involved in the EDRF and NO actions might be different.
基金the National Natural Science Foundation of China，Natural Science Foundation of Jiangsu Province，Medical Key Personnel of Jiangsu Province，Top Qualified Personnel in Six Fields of Jiangsu Province (006) to WANG Ru-xing and the American Diabetes Association Junior Faculty Awards
文摘Background Diabetes mellitus is associated with coronary dysfunction, contributing to a 2- to 4-fold increase in the risk of coronary heart diseases. The mechanisms by which diabetes induces vasculopathy involve endothelial-dependent and -independent vascular dysfunction in both type 1 and type 2 diabetes mellitus. The purpose of this study is to determine the role of vascular large conductance Ca2＋-activated K＋ （BK） channel activities in coronary dysfunction in streptozotocin-induced diabetic rats. Methods Using videomicroscopy, immunoblotting, fluorescent assay and patch clamp techniques, we investigated the coronary BK channel activities and BK channel-mediated coronary vasoreactivity in streptozotocin-induced diabetic rats. Results BK currents （defined as the iberiotoxin-sensitive K＋ component） contribute （65＋4）% of the total K＋currents in freshly isolated coronary smooth muscle cells and 〉50% of the contraction of the inner diameter of coronary arteries from normal rats. However, BK current density is remarkably reduced in coronary smooth muscle cells of streptozotocin-induced diabetic rats, leading to an increase in coronary artery tension. BK channel activity in response to free Ca2＋ iS impaired in diabetic rats. Moreover, cytoplasmic application of DHS-1 （a specific BK channel i~ subunit activator） robustly enhanced the open probability of BK channels in coronary smooth muscle cells of normal rats. In diabetic rats, the DHS-1 effect was diminished in the presence of 200 nmol/L Ca2＋ and was significantly attenuated in the presence of high free calcium concentration, i.e., 1 μmol/L Ca2＋. Immunoblotting experiments confirmed that there was a 2-fold decrease in BK-β1 protein expression in diabetic vessels, without alterinq the BK channel a-subunit expression.Although the cytosolic Ca2＋ concentration of coronary arterial smooth muscle cells was increased from （103±23） nmol/L （n=5） of control rats to （193±22） nmol/L （n=6, P 〈0.05） of STZ-induced diabetic rats, reduced BK-β1 expression made these channels less sensitive to intracellular Ca2＋, which in turn led to enhanced smooth muscle contraction. Conclusions Our results indicated that BK channels are the key determinant of coronary arterial tone. Impaired BK channel function in diabetes mellitus is associated with down-regulation of BK-β1 expression and reduction of the β1-mediated BK channel activation in diabetic vessels.
基金This work was supported by the National Natural Science Foundation of China (No. 39370270)the Natural Science Foundation of Educational Department of Sichuan Province (No. 2003A058).
