Na/K pump-induced [Na]i gradients in rat ventricular myocytes measured with two-photon microscopy

Sanda Despa, Jens Kockskämper, Lothar A. Blatter, Donald M Bers

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

Via the Na/Ca and Na/H exchange, intracellular Na concentration ([Na] i) is important in regulating cardiac Ca and contractility. Functional data suggest that [Na]i might be heterogeneous in myocytes that are not in steady state, but little direct spatial information is available. Here we used two-photon microscopy of SBFI to spatially resolve [Na]i in rat ventricular myocytes. In vivo calibration yielded an apparent Kd of 27 ± 2 mM Na. Similar resting [Na]i was found using two-photon or single-photon ratiometric measurements with SBFI (10.8 ± 0.7 vs. 11.1 ± 0.7 mM). To assess longitudinal [Na] i gradients, Na/K pumps were blocked at one end of the myocyte (locally pipette-applied K-free extracellular solution) and active in the rest of the cell. This led to a marked increase in [Na]i at sites downstream of the pipette (where Na enters the myocyte and Na/K pumps are blocked). [Na]i rise was smaller at upstream sites. This resulted in sustained [Na]i gradients (up to ∼17 mM/120 μm cell length). This implies that Na diffusion in cardiac myocytes is slow with respect to trans-sarcolemmal Na transport rates, although the mechanisms responsible are unclear. A simple diffusion model indicated that such gradients require a Na diffusion coefficient of 10-12 μm2/s, significantly lower than in aqueous solutions.

Original languageEnglish (US)
Pages (from-to)1360-1368
Number of pages9
JournalBiophysical Journal
Volume87
Issue number2
DOIs
StatePublished - Aug 2004
Externally publishedYes

Fingerprint

Photons
Muscle Cells
Microscopy
Cardiac Myocytes
Calibration
sodium-binding benzofuran isophthalate

ASJC Scopus subject areas

  • Biophysics

Cite this

Na/K pump-induced [Na]i gradients in rat ventricular myocytes measured with two-photon microscopy. / Despa, Sanda; Kockskämper, Jens; Blatter, Lothar A.; Bers, Donald M.

In: Biophysical Journal, Vol. 87, No. 2, 08.2004, p. 1360-1368.

Research output: Contribution to journalArticle

Despa, Sanda ; Kockskämper, Jens ; Blatter, Lothar A. ; Bers, Donald M. / Na/K pump-induced [Na]i gradients in rat ventricular myocytes measured with two-photon microscopy. In: Biophysical Journal. 2004 ; Vol. 87, No. 2. pp. 1360-1368.
@article{7d59d1d687464743b4d51b7154526cf0,
title = "Na/K pump-induced [Na]i gradients in rat ventricular myocytes measured with two-photon microscopy",
abstract = "Via the Na/Ca and Na/H exchange, intracellular Na concentration ([Na] i) is important in regulating cardiac Ca and contractility. Functional data suggest that [Na]i might be heterogeneous in myocytes that are not in steady state, but little direct spatial information is available. Here we used two-photon microscopy of SBFI to spatially resolve [Na]i in rat ventricular myocytes. In vivo calibration yielded an apparent Kd of 27 ± 2 mM Na. Similar resting [Na]i was found using two-photon or single-photon ratiometric measurements with SBFI (10.8 ± 0.7 vs. 11.1 ± 0.7 mM). To assess longitudinal [Na] i gradients, Na/K pumps were blocked at one end of the myocyte (locally pipette-applied K-free extracellular solution) and active in the rest of the cell. This led to a marked increase in [Na]i at sites downstream of the pipette (where Na enters the myocyte and Na/K pumps are blocked). [Na]i rise was smaller at upstream sites. This resulted in sustained [Na]i gradients (up to ∼17 mM/120 μm cell length). This implies that Na diffusion in cardiac myocytes is slow with respect to trans-sarcolemmal Na transport rates, although the mechanisms responsible are unclear. A simple diffusion model indicated that such gradients require a Na diffusion coefficient of 10-12 μm2/s, significantly lower than in aqueous solutions.",
author = "Sanda Despa and Jens Kocksk{\"a}mper and Blatter, {Lothar A.} and Bers, {Donald M}",
year = "2004",
month = "8",
doi = "10.1529/biophysj.103.037895",
language = "English (US)",
volume = "87",
pages = "1360--1368",
journal = "Biophysical Journal",
issn = "0006-3495",
publisher = "Biophysical Society",
number = "2",

}

TY - JOUR

T1 - Na/K pump-induced [Na]i gradients in rat ventricular myocytes measured with two-photon microscopy

AU - Despa, Sanda

AU - Kockskämper, Jens

AU - Blatter, Lothar A.

AU - Bers, Donald M

PY - 2004/8

Y1 - 2004/8

N2 - Via the Na/Ca and Na/H exchange, intracellular Na concentration ([Na] i) is important in regulating cardiac Ca and contractility. Functional data suggest that [Na]i might be heterogeneous in myocytes that are not in steady state, but little direct spatial information is available. Here we used two-photon microscopy of SBFI to spatially resolve [Na]i in rat ventricular myocytes. In vivo calibration yielded an apparent Kd of 27 ± 2 mM Na. Similar resting [Na]i was found using two-photon or single-photon ratiometric measurements with SBFI (10.8 ± 0.7 vs. 11.1 ± 0.7 mM). To assess longitudinal [Na] i gradients, Na/K pumps were blocked at one end of the myocyte (locally pipette-applied K-free extracellular solution) and active in the rest of the cell. This led to a marked increase in [Na]i at sites downstream of the pipette (where Na enters the myocyte and Na/K pumps are blocked). [Na]i rise was smaller at upstream sites. This resulted in sustained [Na]i gradients (up to ∼17 mM/120 μm cell length). This implies that Na diffusion in cardiac myocytes is slow with respect to trans-sarcolemmal Na transport rates, although the mechanisms responsible are unclear. A simple diffusion model indicated that such gradients require a Na diffusion coefficient of 10-12 μm2/s, significantly lower than in aqueous solutions.

AB - Via the Na/Ca and Na/H exchange, intracellular Na concentration ([Na] i) is important in regulating cardiac Ca and contractility. Functional data suggest that [Na]i might be heterogeneous in myocytes that are not in steady state, but little direct spatial information is available. Here we used two-photon microscopy of SBFI to spatially resolve [Na]i in rat ventricular myocytes. In vivo calibration yielded an apparent Kd of 27 ± 2 mM Na. Similar resting [Na]i was found using two-photon or single-photon ratiometric measurements with SBFI (10.8 ± 0.7 vs. 11.1 ± 0.7 mM). To assess longitudinal [Na] i gradients, Na/K pumps were blocked at one end of the myocyte (locally pipette-applied K-free extracellular solution) and active in the rest of the cell. This led to a marked increase in [Na]i at sites downstream of the pipette (where Na enters the myocyte and Na/K pumps are blocked). [Na]i rise was smaller at upstream sites. This resulted in sustained [Na]i gradients (up to ∼17 mM/120 μm cell length). This implies that Na diffusion in cardiac myocytes is slow with respect to trans-sarcolemmal Na transport rates, although the mechanisms responsible are unclear. A simple diffusion model indicated that such gradients require a Na diffusion coefficient of 10-12 μm2/s, significantly lower than in aqueous solutions.

UR - http://www.scopus.com/inward/record.url?scp=4143128690&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=4143128690&partnerID=8YFLogxK

U2 - 10.1529/biophysj.103.037895

DO - 10.1529/biophysj.103.037895

M3 - Article

C2 - 15298938

AN - SCOPUS:4143128690

VL - 87

SP - 1360

EP - 1368

JO - Biophysical Journal

JF - Biophysical Journal

SN - 0006-3495

IS - 2

ER -