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

Spontaneous, rhythmical contractions, or vasomotion, can be recorded from cerebral vessels under both normal physiological and pathophysiological conditions. We investigated the cellular mechanisms underlying vasomotion in the cerebral basilar artery (BA) of Wistar rats. Pressure myograph video microscopy was used to study the changes in cerebral artery vessel diameter. The main results of this study were as follows: (1) The diameters of BA and middle cerebral artery (MCA) were 314.5±15.7 μm (n=15) and 233.3±10.1 μm (n=12) at 10 mmHg working pressure (P<0.05), respectively. Pressure-induced vasomotion occurred in BA (22/28, 78.6%), but not in MCA (4/31, 12.9%) from 0 to 70 mmHg working pressure. As is typical for vasomotion, the contractile phase of the response was more rapid than the relaxation phase; (2) The frequency of vasomotion response and the diameter were gradually increased in BA from 0 to 70 mmHg working pressure. The amplitude of the rhythmic contractions was relatively constant once stable conditions were achieved. The frequency of contractions was variable and the highest value was 16.7±4.7 (n=13) per 10 min at 60 mmHg working pressure; (3) The pressure-induced vasomotion of the isolated BA was attenuated by nifedipine, NFA, 18β-GA, TEA or in Ca(2+)-free medium. Nifedipine, NFA, 18β-GA or Ca(2+)-free medium not only dampened vasomotion, but also kept BA in relaxation state. In contrasts, TEA kept BA in contraction state. These results suggest that the pressure-induced vasomotion of the isolated BA results from an interaction between Ca(2+)-activated Cl(-) channels (CaCCs) currents and K(Ca) currents. We hypothesize that vasomotion of BA depends on the depolarizing of the vascular smooth muscle cells (VSMCs) to activate CaCCs. Depolarization in turn activates voltage-dependent Ca(2+) channels, synchronizing contractions of adjacent cells through influx of extracellular calcium and the flow of calcium through gap junctions. Subsequent calcium-induced calcium release from ryanodine-sensitive stores activates K(Ca) channels and hyperpolarizes VSMCs, which provides a negative feedback loop for regenerating the contractile cycle.
Animals ; Basilar Artery ; cytology ; metabolism ; physiology ; Chloride Channels ; metabolism ; Female ; Male ; Membrane Potentials ; physiology ; Muscle, Smooth, Vascular ; cytology ; metabolism ; Myocytes, Smooth Muscle ; cytology ; metabolism ; Potassium Channels, Calcium-Activated ; metabolism ; Rats ; Rats, Wistar ; Vasoconstriction ; physiology ; Vasodilation ; physiology