Animals ; Calcium ; physiology ; Chloride Channels ; physiology ; Electrophysiological Phenomena ; Male ; Muscle, Smooth, Vascular ; cytology ; physiology ; Myocytes, Smooth Muscle ; physiology ; Pulmonary Artery ; cytology ; physiology ; Rats ; Rats, Wistar

Renin-angiotensin system (RAS) is involved in the regulation of vascular smooth muscle cell (VSMC) tension. Angiotensin II (Ang II) as the main effector molecule of RAS can increase the intracellular Ca concentration and cause VSMCs contraction by activating angiotensin II type 1 receptor (AT1R). The large-conductance Ca- and voltage-activated potassium (BK) channel is an essential potassium channel in VSMCs, playing an important role in maintaining membrane potential and intracellular potassium-calcium balance. The BK channel in VSMCs mainly consists of α and β1 subunits. Functional BKα subunits contain voltage-sensors and Ca binding sites. Hence, increase in the membrane potential or intracellular Ca concentration can trigger the opening of the BK channel by mediating transient K outward current in a negative regulatory manner. However, increasing evidence has shown that although Ang II can raise the intracellular Ca concentration, it also inhibits the expression and function of the BK channel by activating the PKC pathway, internalizing AT1R-BKα heterodimer, or dissociating α and β1 subunits. Under some specific conditions, Ang II can also activate the BK channel, but the underlying mechanism remains unknown. In this review, we summarize the potential mechanisms underlying the inhibitory or activating effect of Ang II on the BK channel, hoping that it could provide a theoretical basis for improving intracellular ion imbalance.
Angiotensin II ; physiology ; Calcium ; physiology ; Humans ; Large-Conductance Calcium-Activated Potassium Channels ; physiology ; Muscle, Smooth, Vascular ; cytology ; Myocytes, Smooth Muscle ; physiology ; Renin-Angiotensin System

Autophagy plays a crucial role in maintaining normal structure and vascular function in vivo. When stress-relevant stimuli are involved, the increases of autophagy can protect vascular smooth muscle cells, promote cell survival, and phenotype transformation, as well as reduce calcification. On the contrary, the decrease of autophagy can accelerate cell senescence, resulting in structural changes and dysfunction of vasomotor and vasodilation. However, excessive activation of autophagy can induce the damage of the healthy protein and essential organelles, and even lead to autophagic cell death, accelerating the progression of vascular disease. Thus, the precise targeting of autophagy opens a novel way for treatment of vascular diseases.
Autophagy ; physiology ; Cell Survival ; Cellular Senescence ; Disease Progression ; Humans ; Muscle, Smooth, Vascular ; cytology ; Myocytes, Smooth Muscle ; physiology ; Vascular Diseases ; pathology ; therapy

Spontaneous transient outward currents (STOCs) play an important role in the myogenic regulation of small artery tone, such as coronary artery. In the present study, we investigated the electrophysiological properties and the regulation of STOCs in vascular smooth muscle cells (VSMCs) of porcine coronary artery by perforated patch-clamp technique. Our data showed that STOCs were dependent on voltage and extracellular calcium and they were highly variable in amplitudes and frequencies. STOCs superimposed stochastically onto whole-cell K(+) currents induced by step and ramp protocols. STOCs were completely abolished by ChTX [inhibitor of large-conductance Ca(2+)-activated potassium (BK(Ca)) channels], removal of extracellular Ca(2+), or addition of ryanodine (50 mumol/L) respectively. In contrast, CdCl2 and verapamil, inhibitors of voltage-dependent L-type Ca(2+) channels, had little effect on STOCs. Caffeine (5 mmol/L) transiently increased STOCs (hump), followed by a temporary inhibition. Ca(2+) ionophore A23187 increased both amplitude and frequency of STOCs. Na(+) ionophore monensin increased the frequency of STOCs. STOCs were strongly inhibited by KB-R7943, a selective inhibitor of the reverse mode of the Na(+)/Ca(2+) exchanger. Based on these observations, we conclude that STOCs are mediated by BK(Ca) channels. The generation and activation of STOCs depend upon Ca(2+) influx through Na(+)/Ca(2+) exchange and release of Ca(2+) from sarcoplasmic reticulum (SR) via ryanodine receptors. This suggests that Na(+)/Ca(2+) exchange determines calcium store refilling. Recycling of entering Ca(2+) from superficial SR may locally elevate Ca(2+) concentration at the plasma membrane, thereby activating BK(Ca) channels and then initiating STOCs.
Animals ; Coronary Vessels ; cytology ; physiology ; Electrophysiological Phenomena ; physiology ; Muscle, Smooth, Vascular ; cytology ; physiology ; Myocytes, Smooth Muscle ; cytology ; physiology ; Patch-Clamp Techniques ; Potassium Channels, Calcium-Activated ; physiology ; Sodium-Calcium Exchanger ; physiology ; Swine

AIMTo study the effects of oxyphenamone (Oxy) on activation of Ca(2+)-activated K+ channels in rabbit mesenteric vascular smooth muscle cells.

METHODSTo measure the effect of Oxy on the Ca(2+)-activated K+ channel (BK (Ca) channel) activity in rabbit mesenteric vascular smooth muscle cells by using whole cell patch clamp techniques.

RESULTSOxy reversibly increase BK (Ca) channel activity in rabbit mesenteric artery smooth muscle cells. Application of Oxy (0.1 mumol.L-1) to the perfusion solution caused significant increase in outward currents and its effect was completely abolished by washout; The outward currents K+ was inhibited by TEA (7.5 mmol.L-1); Oxy activated the BK (Ca) channel in a dose-dependent manner (0.01-10 mumol.L-1).

CONCLUSIONOxy directly increase the activity of BK (Ca) channel activity in rabbit mesenteric vascular smooth muscle cells in dose-dependent manner.

Animals ; Cardiotonic Agents ; pharmacology ; Mesenteric Arteries ; cytology ; Muscle, Smooth, Vascular ; cytology ; Myocytes, Smooth Muscle ; physiology ; Organic Chemicals ; Patch-Clamp Techniques ; Potassium Channels, Calcium-Activated ; drug effects ; Rabbits

The changes in potassium currents of vascular smooth muscle cells (VSMCs) isolated from saphenous arteries and the 2nd-6th order branches of the mesenteric arteries of 4-week tail-suspended rats (SUS) were examined using whole cell patch clamp technique. The resting potential (RP) of the VSMCs from SUS group was more negative compared with that of the control group (CON).The whole cell potassium current densities of VSMCs isolated from the saphenous arteries and small mesenteric arteries in SUS group were significantly larger than those of the CON group.The BK(Ca) and K(V) current densities of VSMCs from saphenous arteries and small mesenteric arteries from SUS group were also significantly larger than those from the CON group.It is speculated that the hyperpolarization of VSMCs and decreased calcium influx through voltage-dependent calcium channels might be one of the electrophysiological mechanisms involved in the depressed vasoreactivity of hindquarter arteries induced by simulated weightlessness.
Animals ; Arteries ; cytology ; Male ; Muscle, Smooth, Vascular ; cytology ; Myocytes, Smooth Muscle ; metabolism ; Patch-Clamp Techniques ; Potassium ; metabolism ; Potassium Channels, Calcium-Activated ; physiology ; Rats ; Rats, Sprague-Dawley ; Weightlessness Simulation

OBJECTIVETo evaluate the roles of Na+/H+ exchanger-1 (NHE-1) in the proliferation and apoptosis of pulmonary artery smooth muscle cells in rats.

METHODSTwenty Wistar rats were randomized into control group and 3-week hypoxic group. Intracellular pH (pHi) of the smooth muscle was determined with fluorescence measurement of the pH-sensitive dye BCECF-AM, and the expression of NHE-1 mRNA was detected by reverse transcription polymerase chain reaction (RT-PCR). Primary culture of pulmonary artery smooth muscle cells in vitro was performed. In situ cell death detection kit (TUNEL) was used for studying the effect of specific NHE-1 inhibitor-dimethyl amiloride (DMA) on the apoptosis of muscle cells which had intracellular acidification.

RESULTSpHi value and NHE-1 mRNA expression of pulmonary artery smooth muscle cells were significantly higher in the hypoxic group than in the control group (P < 0.01, P < 0.001). DMA elevated the apoptotic ratio remarkably. The effect was enhanced when DMA concentration increased and the time prolonged.

CONCLUSIONSWith the function of adjusting pHi, NHE-1 may play an important role in the proliferation and apoptosis of pulmonary artery smooth muscle cells.

Animals ; Apoptosis ; Cell Division ; Male ; Muscle, Smooth, Vascular ; cytology ; Pulmonary Artery ; cytology ; Rats ; Rats, Wistar ; Sodium-Hydrogen Exchangers ; physiology

OBJECTIVETo investigate the difference in membrane current of vascular smooth muscle cells (VSMCs) in brain artery (BA) of spontaneously hypertensive rats (SHR) and Wistar rats.

METHODSWe compared the properties of spontaneous transient outward K+ currents (STOCs), the density and composition of current of VSMCs in BA of SHR and Wistar rats by whole-cell patch clamp technique.

RESULTS(1) When the command voltage was 0, + 20, + 40 and + 60 mV respectively, the current densities of VSMCs in BA of SHR and Wistar rats were significant different (P < 0.01). (2) The whole-cell current of VSMCs was partly inhibited by 1 mmol/L4-AP (voltage-gated K+ channel blocker) or 1 mmol/L TEA (big conductance Ca(2+)-activated K+ channel blocker) respectively. (3) The frequency and amplitude of STOCs in SHR were faster and bigger than those in Wistar rats. 1 mmol/L TEA almostly inhibited the STOCs, but not by 4-AP.

CONCLUSIONThese results suggest that the current densities of VSMCs in BA of SHR and Wistar rats are significant different, the outward current of VSMCs in BA of SHR and Wistar rats are composed by Kv and BK(Ca). SHR express more STOCs mediated by BK(Ca), than Wistar rats.

Animals ; Cerebral Arteries ; cytology ; physiology ; Membrane Potentials ; physiology ; Muscle, Smooth, Vascular ; cytology ; physiology ; Myocytes, Smooth Muscle ; physiology ; Patch-Clamp Techniques ; Potassium Channels, Calcium-Activated ; physiology ; Potassium Channels, Voltage-Gated ; physiology ; Rats ; Rats, Inbred SHR ; Rats, Wistar

OBJECTIVETo investigate the effects of pH0 on the electrophysiological properties of vascular smooth muscle cells (VSMCs) in brain artery of spontaneously hypertension rats (SHR).

METHODSWe studied the effects and the ion mechanism of pH0 on whole-cell membrane current of VSMCs in brain artery of 200 - 250 g SHR by whole-cell patch clamp recordings.

RESULTS1. Acidic pH0 could inhibit the outward current of VSMCs of brain artery in SHR in a voltage-dependent manner. It induced a more pronounced inhibition of the outward current from 0 to + 60mV; 2. In the presence of 1 mmol/L TEA, the inhibition of acidic pH0 on the outward current of VSMCs of brain artery was inhibited.

CONCLUSIONThe changes of outward current of VSMCs of brain artery in SHR induced by pH0 may be connected with BKCa channel.

Animals ; Cerebral Arteries ; cytology ; Electrophysiological Phenomena ; Extracellular Fluid ; physiology ; Hydrogen-Ion Concentration ; Muscle, Smooth, Vascular ; physiology ; Rats ; Rats, Inbred SHR

The objective of this paper was to investigate the effect of mitochondrial ATP-sensitive K(+) (MitoK(ATP)) channels on the expression of hypoxia inducible factor-1alpha (HIF-1alpha) and cell proliferation in pulmonary arterial smooth muscle cells (PASMCs) of rats. Cultured PASMCs were divided into six groups as follows: (1) normoxia group: cultured under normoxia for 24 h; (2) normoxia + diazoxide group: cultured under normoxia with diazoxide, an opener of MitoK(ATP) channel, for 24 h; (3) normoxia + 5-HD group: cultured under normoxia with 5-hydroxydecanoate (5-HD), an antagonist of MitoK(ATP) channel, for 24 h; (4) hypoxia group: cultured under hypoxia (37 degrees C, 5% O(2), 5% CO(2), 90% N(2)) for 24 h; (5) hypoxia + diazoxide group: cultured under hypoxia (37 degrees C, 5% O(2), 5% CO(2), 90% N(2)) with diazoxide for 24 h; (6) hypoxia + 5-HD group: cultured under hypoxia (37 degrees C, 5% O(2), 5% CO(2), 90% N(2)) with 5-HD for 24 h. The relative changes in mitochondrial potential were tested with Rhodamine 123 (R-123) fluorescence technique. Immunohistochemical method was used to trace the expression of HIF-1alpha. The proliferation of PASMCs was examined by MTT colorimetric assay. The results were as follows: The intensity of R-123 fluorescence in normoxia + diazoxide group was significantly increased as compared with that in normoxia group (P<0.05), and the intensity of R-123 fluorescence in hypoxia + diazoxide group was also significantly increased as compared with that in hypoxia group (P<0.05). 24-hour hypoxia or 24-hour hypoxia + diazoxide markedly increased the intensity of R-123 fluorescence in PASMCs as compared with normoxia (P<0.05), and the change was more prominant in hypoxia + diazoxide group than that in hypoxia group (P<0.05). There was no significant difference in the intensity of R-123 fluorescence between normoxia group and normoxia + 5-HD group (P>0.05). However, 5-HD weakened the effect of 24-hour hypoxia on the intensity of R-123 fluorescence. The intensity of R-123 fluorescence in hypoxia + 5-HD group was significantly decreased as compared with that in hypoxia group (P<0.05). After exposure to hypoxia or hypoxia + diazoxide for 24 h, the expression of HIF-1alpha and the proliferation of PASMCs were significantly increased as compared with that in normoxia or normoxia + diazoxide group (P<0.05), and the change was more significant in hypoxia + diazoxide group than that in hypoxia group (P<0.05). There was no significant difference in the expression of HIF-1alpha and the proliferation of PASMCs between normoxia group and normoxia + 5-HD group (P>0.05). However, the expression of HIF-1alpha and the proliferation of PASMCs in hypoxia + 5-HD group were significantly decreased as compared with that in hypoxia group (P<0.05). All these results suggest that the opening of MitoK(ATP) channels followed by a depolarization of mitochondrial membrane might contribute to the increase of the expression of HIF-1alpha and the proliferation of PASMCs. This might be a mechanism of the development of hypoxic pulmonary hypertension.
Animals ; Cell Hypoxia ; Cell Proliferation ; Cells, Cultured ; Hypoxia-Inducible Factor 1, alpha Subunit ; metabolism ; Male ; Muscle, Smooth, Vascular ; cytology ; physiology ; Myocytes, Smooth Muscle ; cytology ; physiology ; Potassium Channels ; physiology ; Pulmonary Artery ; cytology ; physiology ; Rats ; Rats, Sprague-Dawley