On the relationship between $$\dot V_{\max }$$ of slow responses and Ca-current availability in whole-cell clamped guinea pig heart cells

1987 ◽  
Vol 410 (1-2) ◽  
pp. 15-22 ◽  
Author(s):  
C. O. Mal�cot ◽  
W. Trautwein
Keyword(s):  
Guinea Pig ◽  
Heart Cells ◽  
Ca Current ◽  
Guinea Pig Heart ◽  
Whole Cell ◽  
Current Availability ◽  
The Relationship

Contraction and sarcoplasmic reticulum Ca2+ content in single myocytes of guinea pig heart: effect of ryanodine

1990 ◽  
Vol 259 (4) ◽  
pp. H1222-H1229 ◽  
Author(s):  
B. Lewartowski ◽  
R. G. Hansford ◽  
G. A. Langer ◽  
E. G. Lakatta
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Guinea Pig ◽  
Time Course ◽  
Ventricular Myocardium ◽  
Short Exposure ◽  
Isolated Cells ◽  
Guinea Pig Heart ◽  
Time To Peak ◽  
The Relationship ◽  
Steady State Amplitude

The relationship between the ability of sarcoplasmic reticulum (SR) to accumulate and retain Ca2+ and the electrically stimulated contractions (ESCs) of isolated cells from guinea pig ventricular myocardium was investigated. Caffeine contractures or rapid cooling contractures were used as a relative measure of the SR Ca2+ content. Depletion of SR Ca2+ by short exposure to caffeine (15 mM) or by prolonged rest resulted in a reduction of the amplitude of the ESCs by 83 +/- 14 and 65 +/- 11% (means +/- SD), respectively. This result points to SR as a major source of the Ca2+ that activates contraction. However, depriving the SR of the ability to retain Ca2+ by means of prolonged (up to 75 min) exposure to 0.1 microM ryanodine (as shown by the absence of contractile response to caffeine or cooling) did not prevent an ESC of nearly normal amplitude (81 +/- 24% control), albeit with a reduced contraction velocity and a time to peak contraction prolonged by 51 +/- 11%. Additionally, while rest decay of ESCs was present after ryanodine treatment, the time for the ESCs to recover their steady-state amplitude was prolonged at least twofold. Thus, in contrast with the normal guinea pig cells, ESCs of the myocytes exposed to ryanodine are controlled by sarcolemmal processes. This change in the state of excitation-contraction coupling results mainly in modification of the time course of the ESCs and of the time course of the response of the cells to the change in the rate of stimulation.

Intracellular Ca2+ and protein kinase C modulate K+ current in guinea pig heart cells

1987 ◽  
Vol 253 (5) ◽  
pp. H1321-H1324 ◽  
Author(s):  
N. Tohse ◽  
M. Kameyama ◽  
H. Irisawa
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Guinea Pig ◽  
Cell Voltage ◽  
Delayed Rectifier ◽  
Heart Cells ◽  
Guinea Pig Heart ◽  
Kinase C ◽  
Ventricular Cells ◽  
K Current

Effects of protein kinase C (PKC) and intracellular calcium ion (Cai2+) on the delayed rectifier K+ current (IK) were investigated in the single ventricular cells of guinea pig by use of an internal-dialysis method and a whole cell voltage-clamp technique. 12-O-tetradecanoylphorbol-13-acetate (TPA, 10(-9) M), an activator of PKC, increased the amplitude of IK in the presence of Cai2+ higher than 10(-10) M. This effect of TPA was mimicked by a synthetic diacylglycerol, 1-oleoyl-2-acetylglycerol (OAG), 50 micrograms/ml, 125 microM, and was blocked by 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (10 microM). The above findings suggest that IK channels were phosphorylated by PKC and thereby the amplitude of IK was increased. IK was also increased by elevating the concentration of Cai2+ in the absence of TPA. It is thus indicated that IK channels are modulated by Cai2+ not only through activation of PKC but also directly. Our observation may provide a possible mechanism by which Cai2+ mediates the link between the Ca2+ transients during contraction and the action potential duration.

scholarly journals Characterization of the inhibition by stilbene disulphonates and phloretin of lactate and pyruvate transport into rat and guinea-pig cardiac myocytes suggests the presence of two kinetically distinct carriers in heart cells

1993 ◽  
Vol 290 (1) ◽  
pp. 249-258 ◽  
Author(s):  
X Wang ◽  
R C Poole ◽  
A P Halestrap ◽  
A J Levi
Keyword(s):  
Guinea Pig ◽  
Cardiac Myocytes ◽  
Rat Heart ◽  
Heart Cells ◽  
Perfused Heart ◽  
Maximal Inhibition ◽  
Guinea Pig Heart ◽  
Concentration Maximum ◽  
Lactate And Pyruvate ◽  
Rat Heart Cells

1. The kinetics of transport of pyruvate (Km 0.20 mM), L-lactate (Km 2.2 mM) and D-lactate (Ki 10.2 mM) into rat cardiac myocytes were studied and compared with those for guinea-pig heart cells [Poole, Halestrap, Price and Levi (1989) Biochem. J. 264, 409-418] whose equivalent values were 0.07, 2.3 and 6.6 mM respectively. Maximal rates of transport were about 5-fold higher in the rat heart cells. 2. 4,4′-Dibenzamidostilbene-2,2′-disulphonate (DBDS), a powerful inhibitor of monocarboxylate transport into erythrocytes [Poole & Halestrap (1991) Biochem. J. 275, 307-312], was found to be a potent but apparently partial inhibitor of lactate and pyruvate transport, with an apparent Ki value at 0.5 mM L-lactate of about 16 microM in both species. Maximal inhibition was 50% and 80% in rat and guinea-pig cells respectively. 3. The maximal extent of inhibition and apparent Ki values were dependent on both the substrate transported and its concentration. Maximum inhibition was less and the Ki was greater at higher substrate concentrations. 4. A variety of other stilbene disulphonates were studied which showed different Ki values and maximal extents of inhibition. 5. Phloretin was a significantly less potent inhibitor of transport into both rat (Ki 25 microM) and guinea-pig (Ki 16 microM) heart cells than into rat erythrocytes (Ki 1.4 microM). In the rat but not the guinea-pig heart cells, inhibition appeared partial (maximal inhibition 84%). 6. We demonstrate that our results can be explained by the presence of two monocarboxylate carriers in heart cells, both with Km values for L-lactate of about 2 mM and inhibited by alpha-cyano-4-hydroxycinnamate, but with different affinities for other substrates and inhibitors. One carrier is sensitive to inhibition by stilbene disulphonates and has lower Km values for pyruvate (0.05-0.10 mM) and D-lactate (5 mM), whereas the other has higher Km values for pyruvate (0.30 mM) and D-lactate (25 mM), and is relatively insensitive to stilbene disulphonates. Rat heart cells possess more of the latter carrier and guinea-pig heart cells more of the former. 7. The significance of these results for the study of lactate transport in the perfused heart is discussed.

scholarly journals Inability of endothelin to increase Ca2+ current in guinea-pig heart cells

1990 ◽  
Vol 99 (3) ◽  
pp. 437-438 ◽  
Author(s):  
Noritsugu Tohse ◽  
Yuichi Hattori ◽  
Haruaki Nakaya ◽  
Masayuki Endou ◽  
Morio Kanno
Keyword(s):  
Guinea Pig ◽  
Heart Cells ◽  
Guinea Pig Heart
Sign in / Sign up

Export Citation Format

Share Document