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Aim To investigate the effect of dapagliflozin on the small conductance calcium-activated potassium channel 2 (SK2 channel) protein in the myocardium of diabetic rats and its possible mechanism of action. Methods In vivo: type 2 diabetes model was established by high-glucose and high-fat diet combined with intraperitoneal injection of low-dose streptozotocin (35 mg
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Objective • To observe the effect of protease activated receptor 2 (PAR2) on the colonic motility in diabetic mice and investigate the mechanism. Methods • The mouse model of type 1 diabetes mellitus was established by intraperitoneal injection of streptozotocin. The smooth muscle strips and segments of colons were isolated. The effects of PAR2 agonist on colonic motility were observed by muscle strip tension contraction and colonic migrating motor complex experiments. The effect of small conductance calcium-activated potassium channel (SK3 channel) antagonist on it was also observed. Results • PAR2 agonist inhibited colonic motility and colonic smooth muscle was more sensitive to PAR2 agonist in diabetic mice. PAR2 agonist-induced inhibition was inhibited by SK3 channel antagonist. Conclusion • PAR2 activity in diabetic mice colons is significantly enhanced, which may inhibit colonic motility through SK3 channel.
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Objective The mechanisms of docosahexaenoic acid (DHA) protecting the cardiovascular system have not yet been clarified. This study was to investigate the vasorelaxative effect of 13,14-epoxy docosapentaenoic acid (13,14-EpDPE) on coronary arterioles in normal rats and its action mechanisms.Methods We isolated coronary artery smooth muscle cells (CASMCs) from normal rats by enzyme digestion, examined the open probabilities of the large conductance calcium-activated potassium (BK) channels in inside-out single channel configuration in the presence of different concentrations (0, 1, 10 and 100 pmol/L) of 13,14-EpDPE, and recorded the BK currents with the patch clamp in whole cell configuration. Then we assessed the coronary arterial relaxation by measuring dilatory responses to 13,14-EpDPE in pre-contracted tissues with or without pre-treatment with iberiotoxin.Results In the presence of 0, 1, 10 and 100 pmol/L of 13,14-EpDPE, the open probabilities of the BK channels were 0.25±0.03, 0.34±0.03, 0.44±0.06 and 0.85±0.16 (n=6), respectively, significantly increased at 100 pmol/L as compared with 0, 1 and 10 pmol/L (P<0.05). The BK channels were activated by 13,14-EpDP in a concentration-dependent manner and its half-effect concentration was (15.94±1.21) pmol/L. The current density was increased from (58.27±16.35) to (95.94±23.00) pA/pF (P=0.002) after 10 pmol/L 13,14-EpDP perfusion when the stimulation voltage was 100 mV. 13,14-EpDPE dilated the isolated coronary arterioles in a dose-dependent manner, and its effects were abolished after pre-treatment with iberiotoxin (100 nM).Conclusion 13,14-EpDPE can dilate coronary arterioles by activating BK channels in CASMCs, which might be one of the mechanisms underlying its protective effect on the cardiovascular system.
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Intermediate-conductance Ca2+-activated K+channel ,also known as KCa3.1,IKCa and SK4,is widely distributed in fibroblasts,proliferating smooth muscle cells,endothelial cells,T lymphocytes,plasma cells,macrophages,and epithelial cells, and involved in the pathological and physiological processes such as vascular contraction,inflammation ,calcification,tissue fibrosis, immune response,malignant tumor,internal and external secretory glands. In recent years,it has been found that blocking the KCa3.1 pathway or knockouting the gene can significantly prevent the pathophysiological process of its involvement. The recent use of the specific blocker TRAM-34 in animals and humans shows its safety and tolerability,providing a new direction for the treatment of related diseases. In this article,the research progress in KCa3.1 related diseases in recent years is reviewed.
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Intermediate-conductance Ca2+-activated K+ channel, also known as KCa3.1, IKCa and SK4, is widely distributed in fibroblasts, proliferating smooth muscle cells, endothelial cells, T lymphocytes, plasma cells, macrophages, and epithelial cells, and involved in the pathological and physiological processes such as vascular contraction, inflammation, calcification, tissue fibrosis, immune response, malignant tumor, internal and external secretory glands. In recent years, it has been found that blocking the KCa3.1 pathway or knockouting the gene can significantly prevent the pathophysiological process of its involvement. The recent use of the specific blocker TRAM-34 in animals and humans shows its safety and tolerability, providing a new direction for the treatment of related diseases. In this article, the research progress in KCa3.1 related diseases in recent years is reviewed.
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Neuronal firing patterns and frequencies determine the nature of encoded information of the neurons. Here we discuss the molecular identity and cellular mechanisms of spike-frequency adaptation in central nervous system (CNS) neurons. Calcium-activated potassium (K(Ca)) channels such as BK(Ca) and SK(Ca) channels have long been known to be important mediators of spike adaptation via generation of a large afterhyperpolarization when neurons are hyper-activated. However, it has been shown that a strong hyperpolarization via these KCa channels would cease action potential generation rather than reducing the frequency of spike generation. In some types of neurons, the strong hyperpolarization is followed by oscillatory activity in these neurons. Recently, spike-frequency adaptation in thalamocortical (TC) and CA1 hippocampal neurons is shown to be mediated by the Ca²⁺-activated Cl- channel (CACC), anoctamin-2 (ANO2). Knockdown of ANO2 in these neurons results in significantly reduced spike-frequency adaptation accompanied by increased number of spikes without shifting the firing mode, which suggests that ANO2 mediates a genuine form of spike adaptation, finely tuning the frequency of spikes in these neurons. Based on the finding of a broad expression of this new class of CACC in the brain, it can be proposed that the ANO2-mediated spike-frequency adaptation may be a general mechanism to control information transmission in the CNS neurons.
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Action Potentials , Brain , Central Nervous System , Fires , Neurons , Potassium , Potassium Channels, Calcium-ActivatedABSTRACT
The contractile and diastolic function of smooth muscle cells (SMCs) is closely related to penile erection and erectile dysfunction (ED). In addition to nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), sulfur dioxide (SO2), estrogen receptor (ER), P2Y receptor, perivascular tissue (PVT), and calcium activated potassium channel (Kca) are found to be involved in the relaxation of SMCs. This review updates the mechanisms of the relaxation of SMCs and its relationship with ED.
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Humans , Male , Carbon Monoxide , Physiology , Erectile Dysfunction , Hydrogen Sulfide , Metabolism , Muscle Contraction , Muscle, Smooth , Myocytes, Smooth Muscle , Physiology , Nitric Oxide , Physiology , Penile Erection , Physiology , Potassium Channels, Calcium-Activated , Physiology , Receptors, Estrogen , Physiology , Receptors, Purinergic P2Y , Physiology , Sulfur Dioxide , MetabolismABSTRACT
Background Diabetic retinopathy (DR) is a common microvascular complications of the retina,retinal vascular smooth muscle cells of large conductance calcium-activated potassium channels (BK) is a major factor in regulating vasomotor and hemodynamic.Currently,functional changes of BK channel in retinal artery smooth muscle cells (RASMCs) and its role in DR were rarely reported.Objective This study was to investigate the early vascular damage mechanisms in DR by detecting the changes of BK channels current,calcium concentration and open probability (NP0) of BK channel with different calcium concentration in RASMCs of normal and diabetic rats.Method Fifty SPF SD 8-12 weeks old rats were randomly divided into normal control group and diabetic model group.Forty diabetic rats was intraperitoneally injected with 60 mg/kg streptozotocin to form type 1 diabetic model,10 rats (the normal control group) were injected sodium citrate solution with the same manner.Fluorescent probe was applied to detect calcium concentration in rat RASMCs;RASMCs were isolated by using enzyme digestion,and BK-channel electric currents and calcium concentrations in the RASMCs were measured by whole-cell patch clamp technique and fluorescence assay,respectively.The NP0 of BK channel was measured by single patch clamp technique.Results Diabetic models were successfully established in 36 rats with the success rate 90％.When stimulation voltage is greater than 60 mV,the current density of BK channel in RASMCs of diabetic model group decreased;when stimulating voltage was 100 mV,the BK channel currents of RASMCs in the normal control group and diabetic model group were (100±23) PA/PF and (50 ± 7) PA/PF,the difference was statistically significant (t =19.80,P ＜ 0.05).After adding specific BK channel blocker African scorpion toxin 100 nmol,the BK channel current in the normal control group significantly reduced,and that in the diabetes model group was not significantly changed;the calcium ion concentrations in RASMCs were (123±11)nmol/L and (255± 10)nmol/L in the normal control group and diabetic model group,the difference was statistically significant (t =32.50,P＜0.05).When stimulation voltage was 60 mV,with increasing calcium ion concentration,the NP0 of BK channel increased (F =15.28,P＜0.05).Conclusions The electric current and NP0 of BK-channel are obviously reduced and the calcium concentration is evidently elevated in RASMCs of diabetic rats,suggesting that the abnormal of BK-channel is probably one of the important causes of retinal artery abnormal contraction in diabetic rats.
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Objective To study the effects of hydrogen dioxide (oxygen free radical donator) and vitamin C (oxygen free radical scavenger) on the electric current of large conductance calcium -activated potassium channels (BKCa channels) in isolated outer hair cells in aging guinea pigs .Methods Acute enzyme was used to isolat outer hair cells of aging guinea pigs ,in which of BKCa channel's electric current was observed and recorded by whole-cell recording mode of patch -clamp .After recording the stable and normal electric current of BKCa channels ,added H2 O2 dilution (0 .2 mmol/L) 40 μl in the 2 ml chambers within freshly isolated outer hair cells so that the concen‐tration of H2 O2 in the balneum would be 4 μmol /L .The groups(n=5) received individually vitamin C solution (5 mg/ml) 0 ,10 ,20 ,40μl in the 2 ml chambers within freshly isolated outer hair cells so that the concentration of vi‐tamin C in the balneum would be 0 ,25 ,50 ,100 μg /ml ,observing and recording the effects of different concentration of vitamin C to electric current of BKCa channels .Results ①In the w hole-cell mode of patch -clamp ,the rapid activation and non-deactivation electric current with a string of large amplitude was recorded ,above -40~ -30 mV activation voltage .The electric current increased with the increasing membrane potential .The amplitude in‐creased continuously and performed characteristics of outward rectification .When the concentration of IbTX was 100 nmol /L ,the activity of the channel was completely blocked and confirmed BKCa channel's electric current .②Medication within three minutes ,when VT was +50 mV ,the BKCa channels'the maximum peak current densities of 4 μmol /L H2 O2 group rose from 22 .09 ± 0 .27 PA /PF to 43 .53 ± 1 .09 PA/PF ,amplification was 97 .06% .In H2 O2 4 μmol /L + vitamin C with different concentrations as 25 ,50 ,100 μg/ml groups ,the BKCa channels'elec‐tric current performed about concentration-dependent inhibition ,and electric current's amplitude and peak current density decreased with the increasing concentration of vitamin C ,the I-V curves were reduced .However ,this still could not be recovered to the normal levels .Conclusion The oxygen free radical /BKCa exists in the process .The vitamin C as oxygen free radical scavenger can reverse the process to a large extent .
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OBJECTIVE:To discuss the expression of voltage-gated potassium channel(KV1.3)and calcium activated potassi-um channel(KCa3.1)in peripheral monocyte from patients with coronary artery disease(CAD)and the regulatory effect of simvas-tatin. METHODS:20 patients with CAD and 8 control patients without CAD diagnosed by percutaneous coronary intervention but correlated to risk factor of CAD were enrolled. The expression of KV1.3 mRNA and KCa3.1 mRNA were measured by RT-PCR in 2 groups,and those of CAD group were measured by RT-PCR after 1 month of simvastatin treatment. RESULTS:Compared with control group,mRNA expression of KV1.3 [(1.54±0.08)vs.(0.77±0.06),P<0.01] and KCa3.1 [(1.32±0.08)vs.(1.06±0.06), P<0.05] were significantly increased in CAD group. mRNA expression of KV1.3 was significantly correlated to the concentration of C reactive protein (CRP)(P=0.003)and was decreased by simvastatin for one month [(1.54 ± 0.08)vs.(1.14 ± 0.05),P<0.01]. However,mRNA expression of KCa3.1 was not correlated to the concentration of CRP and simvastatin didn’t affect it’s expression. CONCLUSIONS:KV1.3 and KCa3.1 in peripheral monocytes may be two new markers of CAD. Regulating KV1.3 may be one of mechanisms of statin’s pleiotrophic effect.
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[ ABSTRACT] AIM: To discuss the relevance between the pathogenesis of diabetic gastroparesis and the large-conductance calcium-activated potassium channels ( BKCa ) in gastric smooth muscle cells.METHODS:The SD rats were randomly divided into control group and model group.The gastric smooth muscle cells of the SD rats were enzymatically iso-lated in a low calcium solution containing papain.The current was recorded by patch clamp single channel recording tech-nique.The expression of KCNMA and KCNMB1 were observed by the method of immunohistochemistry.RESULTS:The value of BKCa single channel conductance was (220.10 ±10.90) pS;the channels had distinct voltage dependent and cal-cium dependent characteristics.In outside-out patch (Vm =+30 mV), the activation of BKCa was blocked by 200 nmol/L IbTX completely.Compared with control group, the open probability and amplitude of current in model group significant-ly increased, while the mean open time and mean close time significantly decreased.Compared with control group, the ex-pression of KCNMB1 in model group was significantly increased.CONCLUSION: Up-regulation of β1-subunit and in-crease in BKCa functional activities may be associated with diabetes gastroparesis in rats.
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Objective To investigate the role of large conductance calcium-activated potassium channels (BK) in neuronal Ca2+ overload following traumatic brain injury (TBI). Methods Neuronal cells of C57BL/6 mouse cortex were collected and cultured. Patch-clamp technique was applied to investigate the changes of intracellular free calcium [Ca2+] i and firing frequency of neuronal action potentials in rest condition or evoked by 100 pA electric current lasting 500 ms after perfusion of Iberiotoxin ( 100 nmmol/L), a BK specific blocker. The cells were divided randomly into experimental group ( plus Iberiotoxin) and control group. Extracellular solution of cultured neurons was further perfused with KCl (20 mmol/L) to induce elevation of [Ca2 +]i and influence of Iberiotoxin ( 100 nmol/L) on amplitude of [Ca2 +] i elevation was determined. Results No significant changes of neuronal spontaneous action potential frequency and [Ca2 +]i were observed in rest condition after perfusion of Iberiotoxin (P＞0.05).However, when evoked by electric current, the frequency of action potential was (10.4 ± 3.0) Hz,which was increased to ( 13.8 ± 3.7 ) Hz after perfusion of Iberiotoxin, with statistical difference (P＜0.05 ). The [Ca2 +] i level was ( 14.21 ± 16.98 ) nmol/Lbefore perfusion with Iberiotoxin but was increased to (44.07 ± 34. 4) nmol/L after perfusion of Iberiotoxin (P ＜ 0.05 ). Extracellular high concentration of KCl increased [Ca2 +] i of neurons, while perfudion of Iberiotoxin further elevated [Ca2 +]i (P ＜ 0.05).Conclusion BK may play an important role in the regulation of neuronal [Ca2+] i and in neuronal Ca2+overload following TBI.
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Objective Large-conductance culcium-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 bleed pressure (BP), can regulate BKCa activity and then elevate blood pressure. Methods Male Spragne-Dawley rats aged 6 weeks were randomized into high salt diet group (HS) and control group, fed with high salt diet (containing 5% NaCi) 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 sobunits 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 these in the control group. Transcriptions of β1 subanit 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 hetween HS and control groups, but BKCa currents of HS group VSMCs were lower than these 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.
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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 BK Ca 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.
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PURPOSE: The aim of this study was to examine how the mRNA and protein levels of calcium activated Kchannel (K(Ca)) and connexin (Cx) change in association with overactive bladder in the bladder mucosae of stress urinary incontinence (SUI) patients. MATERIALS AND METHODS: Twenty SUI patients were included in our study. Bladder mucosae were obtained, with using cold cup biopsy forceps, from the patients suffering with genuine stress urinary incontinence (group 1, n=7), from the patients suffering with SUI along with urgency and frequency (group 2, n=6), and from the patients suffering with mixed incontinence (group 3, n=7). RESULTS: The mRNA transcripts of type 2 (SK2) and type 3 (SK3) small conductance K(Ca), Cx26, and Cx43 were highly expressed in the bladder mucosa. The message of large conductance K(Ca)(BK) was significantly decreased in group 3 compared with that in the controls. The SK2 and Cx26 messages in group 3 were also lower than those in groups 1 and 2. In the presence of urge incontinence, the BK and SK2 protein levels were decreased and the Cx26 protein expression was significantly increased in the bladder mucosa of the SUI patients. In contrast, there were no significant differences in the mRNA and protein levels of K(Ca)s and Cxs between groups 1 and group 2. CONCLUSIONS: Downregulation of both BK and SK2 and upregulation of Cx26 in the bladder mucosa of MI patients may contribute to the alterations of urothelial instability, and this correlate with the symptom severity of bladder instability in SUI patients.
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Humans , Biopsy , Calcium , Connexin 43 , Connexins , Down-Regulation , Mucous Membrane , Potassium Channels, Calcium-Activated , RNA, Messenger , Surgical Instruments , Up-Regulation , Urinary Bladder , Urinary Bladder, Overactive , Urinary Incontinence , Urinary Incontinence, Stress , Urinary Incontinence, Urge , UrotheliumABSTRACT
AIM: To evaluate the effects of atorvastatin on large-conductance calcium-activated potassium channel(BKCa,MaxiK) of arteria mesenterica minor smooth muscle cells in spontaneously hypertensive rats.METHODS: Twelve male spontaneously hypertensive rats(SHR) aged 9 weeks were randomly divided into atorvastatin treatment group(ATV group,n=6) and distilled water group(DW group,n=6),and 6 Wistar-Kyoto rats were as normal control group(n=6).Atorvastatin and appropriate distilled water were administered to rats in ATV group(50 mg?kg-1?d-1) for 10 weeks by intragastric administration.The changes of abdominal aortic blood pressure were observed and the contents of TC,TG,LDL-C in serum were measured before and after treatment.The arterial mesenterica smooth muscle cell potassium current were recorded using whole cell patch clamp.The BKCa membrane capacitance and its current densitys were detected after the BKCa was blocked using tetraethylammonium.RESULTS: The abdominal aorta blood pressure in ATV group was much lower than that in DW group[(171?8) mm Hg vs(190?10) mm Hg,P
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OBJECTIVE: Tyrosine kinase inhibitors may be useful in the management of cerebral vasospasm. It has not yet reported whether potassium channel plays a role in tyrosine kinase inhibitors-induced vascular relaxation of cerebral artery. This study is undertaken to clarify the role of potassium channel in tyrosine kinase inhibitors-induced vascular relaxation, and to investigate the effect of tyrosine kinase inhibitors on outward potassium currents in freshly isolated smooth muscle cells from rat basilar artery. METHODS: The isolation of rat basilar smooth muscle cells was performed by special techniques. The whole cell currents were recoreded by whole cell patch clamp technique in freshly isolated smooth muscle cells from rat basilar artery. RESULTS: In present study, genistein(n=10), tyrphostin A-23(n=10), A-25(n=10) 30microM into bath solution increased the amplitude of the outward K+ current which was completely blocked by large conductance calcium-activated potassium channel(BK(Ca)) blocker, iberiotoxin(0.1microM), and calcium chelator, BAPTA, in whole cell mode. In contrast, diadzein 30microM(n=10), inactive analogue of genistein, did not increase the amplitude of the outward K+ current. CONCLUSION: Our results suggest tyrosine kinase inhibitors such as genistein, tyrphostin A-23 and A-25 increase the BK(Ca) channel activity in cerebral basilar smooth muscle cells, thereby contributing to the relaxation of cerebral artery.
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Animals , Rats , Basilar Artery , Baths , Calcium , Cerebral Arteries , Genistein , Muscle, Smooth , Myocytes, Smooth Muscle , Potassium , Potassium Channels , Protein-Tyrosine Kinases , Relaxation , Tyrosine , Vasospasm, IntracranialABSTRACT
Objective To study the modulation alterations of calcium activated potassium channel (Kca) and calcium activated chloride channels (Clca) on detrusor instability(DI) and their roles in DI. Methods The detrusor instability (DI) animal model was established using female Wistar rats. Detrusor strips were obtained from normal and DI rats. The contraction frequency and amplitude of the strips were measured by an in vitro tension test. The actions of channel openers and blockers were studied. Results Spontaneous contraction frequency and amplitude of DI increased significantly. The block of big conductance calcium activated potassium channel(Bkca) by Iberiotoxin resulted in decrease of frequency but increase of amplitude in the control, but only increase of frequency in DI. The opener, NS1619, resulted in decreases of frequency and amplitude in the control, but only decreases of frequency in DI. The block of small conductance Kca (Skca) by apamin resulted in increases of frequency and amplitude in both control and DI groups, but the opener, Chlorzoxazone, resulted in decreases of frequency and amplitude in the control, but only decrease of frequency in DI. The contraction alterations of DI were significantly lower than those of the control no matter Kca was blocked or opened. NFA, a selective Clca blocker, resulted in no significant frequency and amplitude alteration in the control, but significant decrease in DI. Conclusion These results suggested that Kca and Clca play a critical role in the modulation of detrusor contraction, and the down regulation of Kca and up regulation of Clca suggests that disorder of calcium related regulation may play an important role in DI.
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Objective To study the effects of Nitric oxide(NO),Nitric oxide synthases (NOS)on calcium-activated potassium channels (KCa) of mesenteric artery smooth muscle(SMC)between patients with essential hypertension (EH) and normotensive patients.Methods (1)Mesenteric artery branch from 21 EH and 18 normotensive patients respectively was digested by enzyme.Patch clamp technique was used to pull cell-attached and inside-out patches on mesenteric artery SMC from EH.The signal channel open number probability (Po),open dwell-time(To) and close dwell- time(Tc),were recorded.(2)The levels of plasma NO?NOS were measured by colorimetry analysis method.(3)The analysis of linear correlation was performed to estimate the relationship between the levels of plasma NO and Po?To?Tc of KCa of mesenteric artery SMC in the subjects of the two groups.Results (1)Compared to that of normotensive patients,the activities of KCa channels of patients with EH was higher.After adding Ca 2+ to cytoplasm,the Po of KCa channels in normotensive patients increased significantly.But there were few changes in EH group.(2)The levels of plasma NO?NOS were lower in EH group than in control group.(3)Linear correlation analysis showed that the levels of plasma NO were correlated positively with Po?To in normotensive patients,wherese the positive correlation were decreased in EH group.Conclusion The activities of KCa channels of patients with EH increase significantly.but the sensitivity to Ca 2+ decreased.NO?NOS may stimulate the KCa channels of normotensive and EH patients,but they may not be main factors in EH patients.
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The conductance change evoked by step depolarization was studied in primarily cultured rat adrenal chromaffin cells using patch-clamp and capacitance measurement techniques. When we applied a depolarizing pulse to a chromaffin cell, the inward calcium current was followed by an outward current and depolarization-induced exocytosis was accompanied by an increase in conductance trace. The slow inward tail current which has the same time course as the conductance change was observed in current recording. The activation of slow tail current was calcium-dependent. Reversal potentials agreed with Nernst equation assuming relative permeability of Cs+ to K+ is 0.095. The outward current and tail current were blocked by apamin (200 nM) and d-tubocurarine (2 mM). The conductance change was blocked by apamin and did not affect membrane capacitance recording. We confirmed that conductance change after depolarization comes from the activation of the SK channel and can be blocked by application of the SK channel blockers. Consequently, it is necessary to consider blocking of the SK channel during membrane capacitance recording.