The individual N- and C-lobes of calmodulin tether to the Cav1.2 channel and rescue the channel activity from run-down in ventricular myocytes of guinea-pig heart

FEBS Letters ◽  
2014 ◽  
Vol 588 (21) ◽  
pp. 3855-3861 ◽  
Author(s):  
Dongxue Shao ◽  
Meimi Zhao ◽  
Jianjun Xu ◽  
Rui Feng ◽  
Feng Guo ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Ventricular Myocytes ◽  
Channel Activity ◽  
Guinea Pig Heart ◽  
The Individual

Delayed-rectifier potassium channel activity in isolated membrane patches of guinea pig ventricular myocytes

1991 ◽  
Vol 260 (4) ◽  
pp. H1390-H1393 ◽  
Author(s):  
K. B. Walsh ◽  
J. P. Arena ◽  
W. M. Kwok ◽  
L. Freeman ◽  
R. S. Kass
Keyword(s):  
Guinea Pig ◽  
Single Channel ◽  
Ventricular Myocytes ◽  
Outward Current ◽  
Time Dependent ◽  
Delayed Rectifier ◽  
Potential Range ◽  
Ammonium Compound ◽  
Channel Activity ◽  
Patch Clamp Technique

When the patch-clamp technique was used, a slowly activating, time-dependent outward current was identified in both cell-attached and excised membrane patches obtained from guinea pig ventricular myocytes. This macroscopic patch current was present in approximately 50% of patches studied and could be observed both in the presence and absence of unitary single channel activity (i.e., ATP-sensitive K+ channels). The time course of activation of the patch current resembled that of the whole cell delayed-rectifier K+ current (IK) recorded under similar ionic conditions, and the patch current and IK were activated over a similar membrane potential range. The time-dependent patch current could be eliminated when the Nernst potential for K+ equaled that of the pulse voltage. The patch current was inhibited by external addition of the tertiary ammonium compound LY 97241 (50 microM) and was augmented after internal application of the catalytic subunit of adenosine 3',5'-cyclic monophosphate-dependent protein kinase (500 nM). Deactivating tail currents with kinetics similar to those of IK could be recorded to cell-attached and excised patches. Unitary single channel events underlying the time-dependent patch current could not be resolved despite various attempts to increase single channel conductance. Thus our results suggest that a major component of delayed rectification in guinea pig ventricular cells is due to the activity of a high-density, extremely low conductance K+ channel.

scholarly journals Verrucotoxin, a stonefish venom, modulates calcium channel activity in guinea-pig ventricular myocytes

2007 ◽  
Vol 151 (8) ◽  
pp. 1198-1203 ◽  
Author(s):  
K Yazawa ◽  
J-W Wang ◽  
L-Y Hao ◽  
Y Onoue ◽  
M Kameyama
Keyword(s):  
Guinea Pig ◽  
Calcium Channel ◽  
Ventricular Myocytes ◽  
Channel Activity

Calmodulin reverses rundown of L-type Ca2+ channels in guinea pig ventricular myocytes

2004 ◽  
Vol 287 (6) ◽  
pp. C1717-C1724 ◽  
Author(s):  
Jian-Jun Xu ◽  
Li-Ying Hao ◽  
Asako Kameyama ◽  
Masaki Kameyama
Keyword(s):  
Protein Kinase ◽  
Guinea Pig ◽  
Kinase Inhibitors ◽  
Ventricular Myocytes ◽  
Protein Kinase Inhibitors ◽  
Channel Activity ◽  
Dependent Protein ◽  
Dose Dependent ◽  
Inside Out ◽  
Ca2 Channels

Calmodulin (CaM) is implicated in regulation of Ca2+ channels as a Ca2+ sensor. The effect of CaM on rundown of L-type Ca2+ channels in inside-out patch form was investigated in guinea pig ventricular myocytes. Ca2+ channel activity disappeared within 1–3 min and did not reappear when the patch was excised and exposed to an artificial intracellular solution. However, application of CaM (0.03, 0.3, 3 μM) + 3 mM ATP to the intracellular solution within 1 min after patch excision resulted in dose-dependent activation of channel activity. Channel activity averaged 11.2%, 94.7%, and 292.9%, respectively, of that in cell-attached mode. Channel activity in inside-out patch mode was induced by CaM + ATP at nanomolar Ca2+ concentrations ([Ca2+]); however, increase to micromolar [Ca2+] rapidly inactivated the channel activity induced, revealing that the effect of CaM on the channel was Ca2+ dependent. At the 2nd, 4th, 6th, 8th, and 10th minutes after patch excision, CaM (0.75 μM) + ATP induced Ca2+ channel activity to 150%, 100%, 96.9%, 29.3%, and 16.6%, respectively, revealing a time-dependent action of CaM on the channel. CaM added with adenosine 5′-(β,γ-imido)triphosphate (AMP-PNP) also induced channel activity, although with much lower potency and shorter duration. Protein kinase inhibitors KN-62, CaM-dependent protein kinase (CaMK)II 281-309, autocamtide-related CaMKII inhibitor peptide, and K252a (each 1–10 μM) did not block the effect of CaM, indicating that the effect of CaM on the Ca2+ channel was phosphorylation independent. Neither CaM nor ATP alone induced Ca2+ channel activity, showing a cooperative effect of CaM and ATP on the Ca2+ channel. These results suggest that CaM is a crucial regulatory factor of Ca2+ channel basal activity.

Hydrolysis of 2-acyl-sn-glycero-3-phosphocholines in guinea pig heart mitochondria

1990 ◽  
Vol 68 (9) ◽  
pp. 1090-1095
Author(s):  
Ketan Badiani ◽  
Leona Page ◽  
Gilbert Arthur
Keyword(s):  
Fatty Acids ◽  
Guinea Pig ◽  
Molecular Species ◽  
Unsaturated Fatty Acids ◽  
Heart Mitochondria ◽  
Molar Ratio ◽  
Guinea Pig Heart ◽  
Rate Of Hydrolysis ◽  
The Individual ◽  
Hydrolysis Of

Although both 2-acyl-sn-glycero-3-phosphocholine and 1-acyl-sn-glycero-3-phosphocholine may be produced from phosphatidylcholine hydrolysis, studies on the former have lagged behind that of the latter. In this study a lysophospholipase A2 that hydrolyses 2-acyl-sn-glycero-3-phosphocholine has been characterized in guinea pig heart mitochondria. The lysophospholipase A2 activity was not dependent on Ca2+ and was inhibited differentially by saturated and unsaturated fatty acids. This lysophospholipase A2 activity was able to discriminate among different molecular species of 2-acyl-sn-glycero-3-phosphocholines when they were presented individually or in pairs. The order of decreasing rates of hydrolysis of different molecular species of 2-lysophosphatidylcholines, when the substrates were presented singly, was 18:2 > 20:4 > 18:1 > 16:0. A differential inhibition of the rate of hydrolysis of the individual substrates was observed when the substrates were presented in pairs. The degree of inhibition was dependent on the molar ratio of the mixed substrates. The characteristics of the enzyme suggest that involvement in the selective release of fatty acids from mitochondrial phosphatidylcholine would depend on a high selectivity of phospholipase A1 for different molecular species of phosphatidylcholine. A lysophospholipase A1 activity was also characterized in the mitochondria with a distinct acyl specificity from the lysophospholipase A2. Other characteristics of the two lysophospholipases suggest that the two reactions are not catalysed by the same enzyme.Key words: lysophospholipases, mitochondria, fatty acid relase, heart.

Regulation of KATP channels by P2Ypurinoceptors coupled to PIP2 metabolism in guinea pig ventricular cells

2002 ◽  
Vol 282 (2) ◽  
pp. H757-H765 ◽  
Author(s):  
Naoya Oketani ◽  
Masafumi Kakei ◽  
Kotaro Ichinari ◽  
Midori Okamura ◽  
Akihiro Miyamura ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Ventricular Myocytes ◽  
Katp Channels ◽  
Extracellular Atp ◽  
Channel Activity ◽  
Channel Current ◽  
Channel Inhibition ◽  
Ventricular Cells ◽  
Inside Out ◽  
Stimulation Of

We used patch-clamp techniques to elucidate the regulatory mechanisms of ATP-sensitive K+(KATP) channels by stimulation of P2purinoceptors in guinea pig ventricular myocytes. Extracellular ATP at 0.1 mM transiently inhibited by 90.5 ± 5.0% the whole cell KATP channel current evoked by a reduction in intracellular ATP concentration to 0.5 mM and exposure to 30 μM pinacidil. ADP and AMP (both 1 mM) also decreased the current by 42.8 ± 9.3% and 9.4 ± 4.8%, respectively, but adenosine did not, even at 10 mM. ATP-induced channel inhibition was hardly observed in the presence of 0.2 mM suramin, 0.2 mM guanosine 5'- O-(2-thiodiphosphate), or 0.1 mM compound 48/80, whereas it was not influenced by the presence of 0.1 μM staurosporine or 10 mM 1,2-bis(2-aminophenoxy)ethane- N,N,N′,N′-tetraacetic acid in the pipette. In the presence of 10 μM wortmannin or the absence of ATP in the cytosol, the ATP-induced channel inhibition was irreversible. Phosphatidylinositol 4,5-bisphosphate (PIP2) at 0.1 mM in the outside-out patch pipette prevented ATP-induced channel inhibition. The half-maximal internal ATP concentrations for inhibition of channel activity determined in inside-out membrane patches were 13.8 μM in the presence and 1.12 mM in the absence of 0.1 mM ATP at the external side. It is concluded that activity of KATP channels is modulated by extracellular ATP by a mechanism involving P2Y purinoceptors coupled to GTP-binding proteins associated with reduction of the sarcolemmal PIP2 concentration via stimulation of phospholipase C.

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