AJP - Regu Ad Instruments
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Am J Physiol Regul Integr Comp Physiol 275: R2070-R2080, 1998;
0363-6119/98 $5.00
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Hove-Madsen, L.
Right arrow Articles by Tort, L.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Hove-Madsen, L.
Right arrow Articles by Tort, L.
Vol. 275, Issue 6, R2070-R2080, December 1998

Quantification of Ca2+ uptake in the sarcoplasmic reticulum of trout ventricular myocytes

Leif Hove-Madsen, Anna Llach, and Lluis Tort

Department of Physiology and Cell Biology, Faculty of Science, Universitat Autonoma de Barcelona, 08193 Cerdanyola, Barcelona, Spain

We measured Ca2+ uptake by the sarcoplasmic reticulum (SR) in trout ventricular myocytes, measuring indo 1 fluorescence in permeabilized cells or ionic currents in single myocytes subjected to voltage clamp. Titration of the SR Ca2+ pumps with thapsigargin gave a pump site density of 454 pmol/mg cell protein. Lowering the temperature from 20°C to 10 or 5°C reduced the SR Ca2+ uptake rate in permeabilized myocytes by 50 and 63%, respectively. Surprisingly, Ca2+ leak from the SR also decreased with decreasing temperatures. Exposure of single myocytes to 10 mM caffeine (Caf) induced a cell contracture and an inward ionic current. Neither contracture nor current decreased significantly after rest periods of 120 and 320 s. The inward current was due to Ca2+ extrusion by the Na+/Ca2+ exchanger (NCX), and the time integral of the exchange current (INCX) was used to calculate the SR Ca2+ content. This gave a steady-state SR Ca2+ content of 22.5 ± 2.8 amol Ca2+/pF or 750 µM. When the SR was loaded by depolarizing the cell to +50 mV, the Ca2+ content increased with increasing length of the depolarization, reaching a maximum of 52.0 ± 5.9 amol Ca2+/pF. When the cell was depolarized to different voltages for 3 s, a subsequent Caf-induced INCX increased with increasing voltage. At +100 mV, the Ca2+ content was 36.6 ± 3.8 amol/pF, giving a maximal SR Ca2+ uptake rate of 12.2 ± 1.2 amol Ca2+ · pF-1 · s-1 or 417 µM/s. We conclude that maximal SR Ca2+ content and Ca2+ uptake rates can be estimated using specific SR Ca2+ loading protocols. Contrary to the general assumption that contraction in lower vertebrates depends largely on transsarcolemmal Ca2+ fluxes, we found that although the L-type Ca2+ current is insufficient to fully activate contraction, the SR is capable of participating in the regulation of the cytosolic Ca2+ during the excitation-contraction coupling in trout ventricular myocytes.

sodium ion/calcium ion exchange; caffeine; calcium pump; calcium current; lower vertebrate heart ; excitation-contraction coupling


This article has been cited by other articles:


Home page
 Am. J. Physiol. Cell Physiol.Home page
Y. Xie, M. Ottolia, S. A. John, J.-N. Chen, and K. D. Philipson
Conformational changes of a Ca2+-binding domain of the Na+/Ca2+ exchanger monitored by FRET in transgenic zebrafish heart
Am J Physiol Cell Physiol, August 1, 2008; 295(2): C388 - C393.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Regul. Integr. Comp. Physiol.Home page
C. E. Molina, H. Gesser, A. Llach, L. Tort, and L. Hove-Madsen
Modulation of membrane potential by an acetylcholine-activated potassium current in trout atrial myocytes
Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2007; 292(1): R388 - R395.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Regul. Integr. Comp. Physiol.Home page
H. A. Shiels and E. White
Temporal and spatial properties of cellular Ca2+ flux in trout ventricular myocytes
Am J Physiol Regulatory Integrative Comp Physiol, June 1, 2005; 288(6): R1756 - R1766.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Regul. Integr. Comp. Physiol.Home page
L. Hove-Madsen, A. Llach, G. F. Tibbits, and L. Tort
Triggering of sarcoplasmic reticulum Ca2+ release and contraction by reverse mode Na+/Ca2+ exchange in trout atrial myocytes
Am J Physiol Regulatory Integrative Comp Physiol, May 1, 2003; 284(5): R1330 - R1339.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Regul. Integr. Comp. Physiol.Home page
L. Hove-Madsen, A. Llach, and L. Tort
The function of the sarcoplasmic reticulum is not inhibited by low temperatures in trout atrial myocytes
Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2001; 281(6): R1902 - R1906.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Regul. Integr. Comp. Physiol.Home page
L. Hove-Madsen, A. Llach, and L. Tort
Na+/Ca2+-exchange activity regulates contraction and SR Ca2+ content in rainbow trout atrial myocytes
Am J Physiol Regulatory Integrative Comp Physiol, November 1, 2000; 279(5): R1856 - R1864.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Regul. Integr. Comp. Physiol.Home page
L. Hove-Madsen and L. Tort
L-type Ca2+ current and excitation-contraction coupling in single atrial myocytes from rainbow trout
Am J Physiol Regulatory Integrative Comp Physiol, December 1, 1998; 275(6): R2061 - R2069.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Visit Other APS Journals Online