Effect of Napip on K0 activation of the Na-K pump in adult rat cardiac myocytes

1994 ◽  
Vol 266 (1) ◽  
pp. C37-C41 ◽  
Author(s):  
T. A. Kinard ◽  
X. Y. Liu ◽  
S. Liu ◽  
J. R. Stimers
Keyword(s):  
Environmental Factors ◽  
Cardiac Myocytes ◽  
Pump Current ◽  
Apparent Affinity ◽  
Adult Rat ◽  
Cyclic Model ◽  
Pump Activity ◽  
Dose Dependent ◽  
Rat Cardiac Myocytes ◽  
External K

To determine if environmental factors influence the external K (K0) dependence of Na-K pump current (Ip), we systematically varied internal (pipette) Na (Napip) and Na-K pump activity while measuring the K0 dependence in adult rat cardiac myocytes. For each Napip, reactivation of Ip by K0 was dose dependent. The maximal Ip (Ipmax) and apparent affinity for K0 binding to the Na-K pump (K0.5) increased as Napip increased. The results of making an equimolar substitution of tetramethylammonium for K and Cs, and partial Ip inhibition with ouabain, also showed that Ipmax and K0.5 increased as Napip increased. We simulated pump activity as a function of intracellular Na (Nai) and K0 using a cyclic model of the Na-K pump and found that the model predicts K0.5 for K0 binding increases as Na increases, even when the conditions are adjusted by removing pipette K and partial pump inhibition with ouabain.

scholarly journals Phospholemman overexpression inhibits Na+-K+-ATPase in adult rat cardiac myocytes: relevance to decreased Na+ pump activity in postinfarction myocytes

2006 ◽  
Vol 100 (1) ◽  
pp. 212-220 ◽  
Author(s):  
Xue-Qian Zhang ◽  
J. Randall Moorman ◽  
Belinda A. Ahlers ◽  
Lois L. Carl ◽  
Douglas E. Lake ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Cardiac Myocytes ◽  
Messenger Rna ◽  
Fluorescent Protein ◽  
Pump Current ◽  
Relative Level ◽  
Adult Rat ◽  
Rat Myocytes ◽  
Rat Cardiac Myocytes ◽  
Rna Levels

Messenger RNA levels of phospholemman (PLM), a member of the FXYD family of small single-span membrane proteins with putative ion-transport regulatory properties, were increased in postmyocardial infarction (MI) rat myocytes. We tested the hypothesis that the previously observed reduction in Na+-K+-ATPase activity in MI rat myocytes was due to PLM overexpression. In rat hearts harvested 3 and 7 days post-MI, PLM protein expression was increased by two- and fourfold, respectively. To simulate increased PLM expression post-MI, PLM was overexpressed in normal adult rat myocytes by adenovirus-mediated gene transfer. PLM overexpression did not affect the relative level of phosphorylation on serine68 of PLM. Na+-K+-ATPase activity was measured as ouabain-sensitive Na+-K+ pump current (Ip). Compared with control myocytes overexpressing green fluorescent protein alone, Ip measured in myocytes overexpressing PLM was significantly ( P < 0.0001) lower at similar membrane voltages, pipette Na+ ([Na+]pip) and extracellular K+ ([K+]o) concentrations. From −70 to +60 mV, neither [Na+]pip nor [K+]o required to attain half-maximal Ip was significantly different between control and PLM myocytes. This phenotype of decreased Vmax without appreciable changes in Km for Na+ and K+ in PLM-overexpressed myocytes was similar to that observed in MI rat myocytes. Inhibition of Ip by PLM overexpression was not due to decreased Na+-K+-ATPase expression because there were no changes in either protein or messenger RNA levels of either α1- or α2-isoforms of Na+-K+-ATPase. In native rat cardiac myocytes, PLM coimmunoprecipitated with α-subunits of Na+-K+-ATPase. Inhibition of Na+-K+-ATPase by PLM overexpression, in addition to previously reported decrease in Na+-K+-ATPase expression, may explain altered Vmax but not Km of Na+-K+-ATPase in postinfarction rat myocytes.

scholarly journals Down-Regulation of Replication Factor C-40 (RFC40) Causes Chromosomal Missegregation in Neonatal and Hypertrophic Adult Rat Cardiac Myocytes

PLoS ONE ◽  
2012 ◽  
Vol 7 (6) ◽  
pp. e39009 ◽  
Author(s):  
Hirotaka Ata ◽  
Deepa Shrestha ◽  
Masahiko Oka ◽  
Rikuo Ochi ◽  
Chian Ju Jong ◽  
...  
Keyword(s):  
Cardiac Myocytes ◽  
Replication Factor C ◽  
Down Regulation ◽  
Replication Factor ◽  
Adult Rat ◽  
Factor C ◽  
Rat Cardiac Myocytes

Alpha 1b-adrenoceptor-mediated stimulation of Na-K pump current in adult rat ventricular myocytes

1993 ◽  
Vol 264 (4) ◽  
pp. H1315-H1318 ◽  
Author(s):  
A. P. Williamson ◽  
R. H. Kennedy ◽  
E. Seifen ◽  
J. P. Lindemann ◽  
J. R. Stimers
Keyword(s):  
Adrenergic Receptors ◽  
Ventricular Myocytes ◽  
Pump Current ◽  
Peak Effect ◽  
Patch Clamp Technique ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Whole Cell Patch Clamp ◽  
Dose Dependent ◽  
Stimulation Of

The purpose of this study was to determine if myocardial alpha 1a-and/or alpha 1b-adrenoceptors are involved in the increase in Na-K pump current (Ip) elicited by alpha 1-adrenergic agonists. Single rat ventricular myocytes were isolated by enzymatic disaggregation. The whole cell patch-clamp technique was used to examine dose-dependent effects of phenylephrine (PE) on holding current (Ih) and to determine whether observed actions were mediated via alpha 1a-or alpha 1b-adrenergic receptors. To minimize the contribution of transsar-colemmal currents other than Ip to Ih, membrane voltage was held constant -40 mV, and cells were maintained in a Ca-free perfusate containing 1 mM Ba and 0.1 mM Cd. All experiments were conducted in the presence of 3 microM nadolol. PE elicited dose-dependent increases in Ih, with a peak effect of 0.57 +/- 0.03 pA/pF observed at 30 microM. The response to PE was dose dependently inhibited by prazosin and chloroethylclonidine and was totally eliminated by 1 mM ouabain. When used at doses selective for the alpha 1a-subtype, WB4101 failed to significantly antagonize the action of PE. These data suggest that the observed alpha 1-adrenoceptor-mediated increase in Ih in isolated rat ventricular myocytes is the result of an increase in Ip effected via stimulation of alpha 1b-adrenergic receptors.

scholarly journals Modulation of the Na,K-pump function by beta subunit isoforms.

1994 ◽  
Vol 103 (4) ◽  
pp. 605-623 ◽  
Author(s):  
F Jaisser ◽  
P Jaunin ◽  
K Geering ◽  
B C Rossier ◽  
J D Horisberger
Keyword(s):  
Ion Transport ◽  
Pump Current ◽  
Beta Subunit ◽  
Beta Subunits ◽  
Transport Activity ◽  
Apparent Affinity ◽  
Significant Difference ◽  
Ouabain Sensitivity ◽  
External K

To study the role of the Na,K-ATPase beta subunit in the ion transport activity, we have coexpressed the Bufo alpha 1 subunit (alpha 1) with three different isotypes of beta subunits, the Bufo Na,K-ATPase beta 1 (beta 1NaK) or beta 3 (beta 3NaK) subunit or the beta subunit of the rabbit gastric H,K-ATPase (beta HK), by cRNA injection in Xenopus oocyte. We studied the K+ activation kinetics by measuring the Na,K-pump current induced by external K+ under voltage clamp conditions. The endogenous oocyte Na,K-ATPase was selectively inhibited, taking advantage of the large difference in ouabain sensitivity between Xenopus and Bufo Na,K pumps. The K+ half-activation constant (K1/2) was higher in the alpha 1 beta 3NaK than in the alpha 1 beta 1NaK groups in the presence of external Na+, but there was no significant difference in the absence of external Na+. Association of alpha 1 and beta HK subunits produced active Na,K pumps with a much lower apparent affinity for K+ both in the presence and in the absence of external Na+. The voltage dependence of the K1/2 for external K+ was similar with the three beta subunits. Our results indicate that the beta subunit has a significant influence on the ion transport activity of the Na,K pump. The small structural differences between the beta 1NaK and beta 3NaK subunits results in a difference of the apparent affinity for K+ that is measurable only in the presence of external Na+, and thus appears not to be directly related to the K+ binding site. In contrast, association of an alpha 1 subunit with a beta HK subunit results in a Na,K pump in which the K+ binding or translocating mechanisms are altered since the apparent affinity for external K+ is affected even in the absence of external Na+.

Effects of Saponin Monomer 13 of Dwarf Lilyturf Tuber on L-Type Calcium Currents in Adult Rat Ventricular Myocytes

2005 ◽  
Vol 33 (05) ◽  
pp. 797-806 ◽  
Author(s):  
Jin Tao ◽  
Hongyi Wang ◽  
Jiandong Chen ◽  
Huae Xu ◽  
Shengnan Li
Keyword(s):  
Cardiac Myocytes ◽  
Ventricular Myocytes ◽  
Calcium Currents ◽  
Inhibitory Effects ◽  
Patch Clamp Recording ◽  
Inactivation Curve ◽  
Control Value ◽  
Adult Rat ◽  
Cardioprotective Effects ◽  
Rat Cardiac Myocytes

The saponin monomer 13 of dwarf lilyturf tuber (DT-13), one of the saponin monomers of dwarf lilyturf tuber, has been found to have potent cardioprotective effects. In order to investigate the effect of DT-13 on L-type calcium currents ( I Ca,L ), exploring the mechanisms of DT-13's cardioprotective effects, we directly measured the I Ca,L in the adult rat cardiac myocytes exposed to DT-13 using standard whole-cell patch-clamp recording technique. Our results showed that DT-13 exerted inhibitory effects on the I Ca,L of the single adult rat cardiac myocytes. The current density was reduced by about 38% after exposure of the cells to DT-13 (0.1 μM) for 10 minutes, from the control value of 7.46 ± 1.31 pA/pF to 4.25 ± 0.35 pA/pF ( n = 6, p < 0.05). This I Ca,L -inhibiting action of DT-13 was concentration-dependent. DT-13 up-shifted the current-voltage (I-V) curve, but did not significantly affect the half activation potential (V0.5). V0.5 was from -11.8 ± 0.9 mV in the control to -12.6 ± 1.9 mV in the presence of DT-13 at 0.1 μmol/L. DT-13 at 0.1 μM did not markedly affect the activation of I Ca,L , but shifted the inactivation curve of I Ca,L to the left. In combination with previous reports, these results suggest that there might be a close relationship between the cardioprotective effects of dwarf lilyturf tuber and the inhibitory effects of DT-13 on L-type calcium currents.

Oxidation of myoglobin in isolated adult rat cardiac myocytes by 15-hydroperoxy-5,8,11,13-eicosatetraenoic acid

FEBS Letters ◽  
1983 ◽  
Vol 163 (2) ◽  
pp. 292-296 ◽  
Author(s):  
Frederick P. Walters ◽  
Frances G. Kennedy ◽  
Dean P. Jones
Keyword(s):  
Cardiac Myocytes ◽  
Eicosatetraenoic Acid ◽  
Adult Rat ◽  
Rat Cardiac Myocytes
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