This study demonstrates that caveolae, omega-shaped membrane invaginations, are involved in cardiac sodium channel regulation by a mechanism involving the α subunit of stimulatory heterotrimeric G-protein, Gα s , via stimulation cell surface β-adrenergic receptor. Stimulation receptors with 10 μmol/L isoproterenol presence protein kinase A inhibitor increased whole-cell current “direct” cAMP-independent G-protein mechanism. The addition antibodies against caveolin-3 to cell’s cytoplasm...

Voltage-dependent sodium channels from a variety of tissues are known to be phosphorylated by the cAMP-dependent protein kinase, kinase A. However, functional significance channel phosphorylation is not clearly understood. Using whole-cell voltage-clamp techniques, we show that currents (INas) in rabbit cardiac myocytes enhanced isoproterenol (ISO). This enhancement INa ISO 1) holding potential dependent, 2) can mimicked forskolin and dibutyryl cAMP, 3) accompanied an increase rate Na+...

Voltage-gated Nav channels are required for normal electrical activity in neurons, skeletal muscle, and cardiomyocytes. In the heart, Nav1.5 is predominant channel, Nav1.5-dependent regulates rapid upstroke of cardiac action potential. requires precise localization at specialized cardiomyocyte membrane domains. However, molecular mechanisms underlying channel trafficking heart unknown. this paper, we demonstrate that ankyrin-G targeting heart. Cardiomyocytes with reduced display expression,...

Conventional microelectrode recordings combined with enzymatic cell dispersion methods and a single voltage-clamp technique were used to record transmembrane action potentials ionic currents in isolated myocytes excised segments of human right atrium. Recordings the outward current(s), which is responsible for resting potential early repolarization atrium, consistently showed that this tissue has 1) relatively small inwardly rectifying background potassium current (IK1) generates mammalian...

1. Modulation of cardiac sodium currents (INa) by the G protein stimulatory alpha subunit (Gsalpha) was studied using patch-clamp techniques on freshly dissociated rat ventricular myocytes. 2. Whole-cell recordings showed that stimulation beta-adrenergic receptors with 10 microM isoprenaline (isoproterenol, ISO) enhanced INa 68.4 +/- 9.6 % (mean s.e.m.; n = 7, P < 0.05 vs. baseline). With addition 22 microgram ml-1 kinase A inhibitor (PKI) to pipette solution, ISO 30.5 7.0 (n solution...

Spontaneously active single cells have been obtained from the sinus venosus region of bull‐frog, Rana catesbeiana, using an enzymic dispersion procedure involving serial applications trypsin, collagenase and elastase in nominally 0 Ca2+ Ringer solution. These normal action potentials fire spontaneously at a rate very similar to intact venosus. A suction micro‐electrode technique (Hamill, Marty, Neher, Sakmann &amp; Sigworth, 1981; Hume Giles, 1983) has used record spontaneous diastolic...

1. Voltage‐ and time‐dependent outward currents were recorded from relaxed enzymatically isolated smooth muscle cells the rabbit left descending coronary artery using a single pipette voltage clamp technique. The calcium‐activated potassium current was blocked by inclusion of EGTA in solution CdCl2 extracellular bath. 2. Outward elicited with depolarizing steps to potentials positive ‐20 mV. Long (5 s) revealed slow inactivation time constant nearly 3 s at +60 Potassium identified as...

Cardiac sodium channels (voltage-gated Na + channel subunit 1.5) reside in both the plasmalemma and membrane invaginations called caveolae. Opening of caveolar neck permits resident to become functional. In cardiac myocytes, opening can be stimulated by applying β-receptor agonists, which initiates an interaction between stimulatory G protein subunit-α (G s α) caveolin-3. This study shows that, adult rat ventricular a functional α-caveolin-3 occurs, even absence caveolin-binding sequence...

1. Whole-cell Na+ currents (holding potential, -80 mV; test -30 mV) in rat myocytes were inhibited by 8, 9-epoxyeicosatrienoic acid (8,9-EET) a dose-dependent manner with 22+/-4% inhibition at 0.5 microM, 48+/-5% 1 and 73+/-5% 5 microM (mean +/- S.E.M., n = 10, P<0.05 for each dose vs. control). Similar results obtained 5,6-, 11,12-, 14,15-EETs, while 8,9-dihydroxyeicosatrienoic (DHET) was 3-fold less potent arachidonic 10- to 20-fold potent. 2. 8,9-EET produced dose-dependent,...

1. Calcium inward currents were recorded from relaxed enzymatically isolated smooth muscle cells the rabbit epicardial left descending coronary artery using a single‐pipette voltage‐clamp technique. Outward K+ blocked with CsCl‐tetraethylammonium‐filled pipette solutions. 2. Relaxed had maximum diameter of 8.6 +/‐ 0.6 microns and cell length 96.7 3.3 when bathed in 2.5 mM [Ca2+]o. The average resting membrane potential at room temperature was ‐32 10 mV. mean capacitance 18.5 1.7 pF input...

1. The effects of isoprenaline (ISO) on the calcium current (ICa) and delayed rectifier K+ (IK) were examined using a tight-seal whole-cell voltage-clamp technique in single cells from bull-frog atrium to examine ionic mechanism(s) catecholamine-induced action potential shape changes. 2. ISO dose-dependent. Very low doses (5 x 10(-9) M) prolonged potential. Higher (10(-6) increased plateau height, but shortened by accelerating early repolarization phase. 3. IK ICa dose-dependent fashion....

We have developed a model of cardiac atrial electrical activity based on voltage-clamp measurements obtained from single cells isolated the bullfrog atrium. These allowed us to simulate number processes thought be important in action potential initiation, repolarization, and excitation-contraction (EC) coupling process. In this model, cell membrane contains both channel-mediated (Na+, Ca2+, inward rectifier K+, delayed linear background leak) transporter-mediated (Na(+)-K+ pump, Na(+)-Ca2+...

Whole-cell patch-clamp techniques were used to study enzymatically dispersed epicardial coronary artery smooth muscle cells. Depolarizing voltage pulses of 500-millisecond duration from -60 mV (118 mmol/L CsCl, 22 tetraethylammonium chloride, and 5 EGTA pipette solution) elicited inward L-type calcium currents (ICa). When was omitted the solution, an outward current superimposed on current, repolarizing steps produced tail (IT). The amplitude these proportional ICa -30 +50 mV. time course...

1. A single‐microelectrode technique has been used to study the voltage dependence and kinetics of inactivation reactivation a tetrodotoxin‐resistant inward current (ICa) in single cells from bull‐frog atrium. 2. In most cases both can be well described as single‐exponential process. 3. Several different observations indicate that ICa these is controlled by voltage‐dependent current‐dependent processes, demonstrated previously heart (Kass &amp; Sanguinetti, 1984; Lee, Marban Tsien, 1985)...

Individual myocytes were isolated from bullfrog atrium by enzymatic and mechanical dispersion, a one-microelectrode voltage clamp was used to record the slow outward K+ currents. In normal [K+]o (2.5 mM), current tails reverse between -95 -100 mV. This finding, observed 51-mV shift of Erev/10-fold change in [K+]o, strongly suggest that "delayed rectifier" atrial cells is current. current, IK, plays an important role initiating repolarization, it distinct quasi-instantaneous, inwardly...

Previous models of cardiac cellular electrophysiology have been based largely on voltage-clamp measurements obtained from multicellular preparations and often combined data different regions the heart a variety species. We developed model pacemaking comprehensive set single cells isolated one specific tissue type, bullfrog sinus venosus (SV). Consequently, sarcolemmal current densities kinetics are not influenced by secondary phenomena associated with preparations, allowing us to...

An enzymatic dispersion procedure has been developed to obtain viable, spontaneously active single myocytes from cardiac pacemaker tissue: the bullfrog (Rana catesbeiana) sinus venosus. Recordings of time- and voltage-dependent Ca2+ K+ currents have made by using a suction-microelectrode technique. The results show that two interact modulate slope potential. These are: (i) decay delayed rectifier current (ii) activation current. In addition, data strongly suggest tissue does not an inwardly...

1. Experimental measurements and computer simulations have been used in attempts to identify an exchanger current (Iex) generated by electrogenic Na+‐Ca2+ single cells from bull‐frog atrium. 2. Voltage clamp of inward 'slow tail' observed upon repolarization after depolarizing pulses that elicit net Ca2+ currents (ICa) (see Campbell, Giles &amp; Shibata, 1988c), show these slow tails a cationic dependence different ICa. Slow are large prominent normal [Na+]o solutions containing either or...

Leading or primary pacemaker cells located within the rabbit sino-atrial node have been identified by using electrophysiological and pharmacological techniques. Stable intracellular recordings lasting 20-30 min from s. a. reveal three distinct patterns of spontaneous responses: (i) leading pacing; (ii) follower subsidiary (iii) ‘anomalous’ discharge. Our main objective was to measure first detectable effect, effects, acetylcholine on electrical activity in mammalian cells. Trains brief...

1. Voltage clamp studies on single cells from bull-frog atrium have been carried out to study the ion transfer characteristics of calcium current, ICa. In agreement with preliminary results Hume & Giles (1983), a TTX-resistant, 'second transient inward current' was recorded consistently. Its average peak size at 0 mV in 2.5 mM [Ca2+]o Ringer solution approximately -200 pA, and it blocked by Cd2+ La3+ but not tetrodotoxin (TTX, 3 x 10(-6) M). 2. The this current increases 4 times when is...

1. Voltage clamp recordings of the calcium current (ICa) in single myocytes which were enzymatically isolated from bull‐frog atrium show that a genuine reversal flowing through Ca2+ channels can be recorded (ef. Reuter &amp; Scholz, 1977; Lee Tsien, 1982, 1984; Campbell, Giles Shibata, 1988c). In normal 2.5 mM [Ca2+]0 Ringer solution this apparent potential (Erev) is near +50 mV, value well below predicted thermodynamic equilibrium (ECa). 2. None less, Erev shifts with variations...

Nitric oxide mediates nerve-induced hyperpolarization of circular smooth muscle the esophagus. Two mechanisms are proposed to explain this hyperpolarization: an increase in K + current or a decrease Cl- current. These studies test hypothesis that nitric increases K+ esophageal muscle. Three outward currents present cells from opossum One is Ca(2 )-activated (IKCa2 ). This inhibited by charybdotoxin. Whole cell were recorded isolated using whole patch-clamp technique. showed IKCa2+ activated...