Intracellular concentrations of major ions in rat myelinated axens and glia: Calculations based on electron probe x-ray microanalyses

Peter K. Stys, Ellen Lehning, A. J. Saubermann, Richard M. LoPachin

Research output: Contribution to journalArticle

44 Citations (Scopus)

Abstract

Electron probe x-ray microanalysis (EPMA) was used to measure water content (percent water) and dry weight elemental concentrations (in millimoles per kilogram) of Na, K, Cl, and Ca in axoplasm and mitochondria of rat optic and tibial nerve myelinated axons. Myelin and cytoplasm of glial cells were also analyzed. Each anatomical compartment exhibited characteristic water contents and distributions of dry weight elements, which were used to calculate respective ionized concentrations. Free axoplasmic [K+] ranged from ≃155 mM in large PNS and CNS axons to ≃120-130 mM in smaller fibers. Free [Na+] was ≃15-17 mM in larger fibers compared with 20- 25 mM in smaller axons, whereas free [Cl-]was found to be 30-55 mM in all axons. Because intracellular Ca is largely bound, ionized concentrations were not estimated. However, calculations of total (free plus bound) aqueous concentrations of this element showed that axoplasm of large CNS and PNS axons contained ≃0.7 mM Ca, whereas small fibers contained 0.1-0.2 mM. Calculated ionic equilibrium potentials were as follows (in mV): in large CNS and PNS axons, E(K) = -105, E(Na) = 60, and E(Cl) = -28; in Schwann cells, E(K) = -107, E(Na) = 33, and E(Cl) = -33; and in CNS gila, E(K) -99, E(Na) = 36, and E(Cl) = -44. Calculated resting membrane potentials were as follows (in mV, including the contribution of the Na+,K+-ATPase): large axons, about -80; small axons, about -72 to -78; and CNS gila, 91. E(Cl) is more positive than resting membrane potential in PNS and CNS axons and gila, indicating active accumulation. Direct EPMA measurement of elemental concentrations and subsequent calculation of ionized fractions in axons and glia offer fundamental neurophysiological information that has been previously unattainable.

Original languageEnglish (US)
Pages (from-to)1920-1928
Number of pages9
JournalJournal of Neurochemistry
Volume68
Issue number5
StatePublished - May 1997

Fingerprint

Neuroglia
Axons
Rats
X-Rays
Electrons
Ions
X rays
Membrane Potentials
Water content
Water
Fibers
Membranes
Weights and Measures
Tibial Nerve
Mitochondria
Schwann Cells
Optic Nerve
Myelin Sheath
Adenosine Triphosphatases
Optics

Keywords

  • Calcium
  • Chloride
  • Myelinated axon
  • Neuroglia
  • Potassium
  • Schwann cell
  • Sodium

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

Cite this

Intracellular concentrations of major ions in rat myelinated axens and glia : Calculations based on electron probe x-ray microanalyses. / Stys, Peter K.; Lehning, Ellen; Saubermann, A. J.; LoPachin, Richard M.

In: Journal of Neurochemistry, Vol. 68, No. 5, 05.1997, p. 1920-1928.

Research output: Contribution to journalArticle

@article{f5c9e750f0fa47deb3cd50b9034b95db,
title = "Intracellular concentrations of major ions in rat myelinated axens and glia: Calculations based on electron probe x-ray microanalyses",
abstract = "Electron probe x-ray microanalysis (EPMA) was used to measure water content (percent water) and dry weight elemental concentrations (in millimoles per kilogram) of Na, K, Cl, and Ca in axoplasm and mitochondria of rat optic and tibial nerve myelinated axons. Myelin and cytoplasm of glial cells were also analyzed. Each anatomical compartment exhibited characteristic water contents and distributions of dry weight elements, which were used to calculate respective ionized concentrations. Free axoplasmic [K+] ranged from ≃155 mM in large PNS and CNS axons to ≃120-130 mM in smaller fibers. Free [Na+] was ≃15-17 mM in larger fibers compared with 20- 25 mM in smaller axons, whereas free [Cl-]was found to be 30-55 mM in all axons. Because intracellular Ca is largely bound, ionized concentrations were not estimated. However, calculations of total (free plus bound) aqueous concentrations of this element showed that axoplasm of large CNS and PNS axons contained ≃0.7 mM Ca, whereas small fibers contained 0.1-0.2 mM. Calculated ionic equilibrium potentials were as follows (in mV): in large CNS and PNS axons, E(K) = -105, E(Na) = 60, and E(Cl) = -28; in Schwann cells, E(K) = -107, E(Na) = 33, and E(Cl) = -33; and in CNS gila, E(K) -99, E(Na) = 36, and E(Cl) = -44. Calculated resting membrane potentials were as follows (in mV, including the contribution of the Na+,K+-ATPase): large axons, about -80; small axons, about -72 to -78; and CNS gila, 91. E(Cl) is more positive than resting membrane potential in PNS and CNS axons and gila, indicating active accumulation. Direct EPMA measurement of elemental concentrations and subsequent calculation of ionized fractions in axons and glia offer fundamental neurophysiological information that has been previously unattainable.",
keywords = "Calcium, Chloride, Myelinated axon, Neuroglia, Potassium, Schwann cell, Sodium",
author = "Stys, {Peter K.} and Ellen Lehning and Saubermann, {A. J.} and LoPachin, {Richard M.}",
year = "1997",
month = "5",
language = "English (US)",
volume = "68",
pages = "1920--1928",
journal = "Journal of Neurochemistry",
issn = "0022-3042",
publisher = "Wiley-Blackwell",
number = "5",

}

TY - JOUR

T1 - Intracellular concentrations of major ions in rat myelinated axens and glia

T2 - Calculations based on electron probe x-ray microanalyses

AU - Stys, Peter K.

AU - Lehning, Ellen

AU - Saubermann, A. J.

AU - LoPachin, Richard M.

PY - 1997/5

Y1 - 1997/5

N2 - Electron probe x-ray microanalysis (EPMA) was used to measure water content (percent water) and dry weight elemental concentrations (in millimoles per kilogram) of Na, K, Cl, and Ca in axoplasm and mitochondria of rat optic and tibial nerve myelinated axons. Myelin and cytoplasm of glial cells were also analyzed. Each anatomical compartment exhibited characteristic water contents and distributions of dry weight elements, which were used to calculate respective ionized concentrations. Free axoplasmic [K+] ranged from ≃155 mM in large PNS and CNS axons to ≃120-130 mM in smaller fibers. Free [Na+] was ≃15-17 mM in larger fibers compared with 20- 25 mM in smaller axons, whereas free [Cl-]was found to be 30-55 mM in all axons. Because intracellular Ca is largely bound, ionized concentrations were not estimated. However, calculations of total (free plus bound) aqueous concentrations of this element showed that axoplasm of large CNS and PNS axons contained ≃0.7 mM Ca, whereas small fibers contained 0.1-0.2 mM. Calculated ionic equilibrium potentials were as follows (in mV): in large CNS and PNS axons, E(K) = -105, E(Na) = 60, and E(Cl) = -28; in Schwann cells, E(K) = -107, E(Na) = 33, and E(Cl) = -33; and in CNS gila, E(K) -99, E(Na) = 36, and E(Cl) = -44. Calculated resting membrane potentials were as follows (in mV, including the contribution of the Na+,K+-ATPase): large axons, about -80; small axons, about -72 to -78; and CNS gila, 91. E(Cl) is more positive than resting membrane potential in PNS and CNS axons and gila, indicating active accumulation. Direct EPMA measurement of elemental concentrations and subsequent calculation of ionized fractions in axons and glia offer fundamental neurophysiological information that has been previously unattainable.

AB - Electron probe x-ray microanalysis (EPMA) was used to measure water content (percent water) and dry weight elemental concentrations (in millimoles per kilogram) of Na, K, Cl, and Ca in axoplasm and mitochondria of rat optic and tibial nerve myelinated axons. Myelin and cytoplasm of glial cells were also analyzed. Each anatomical compartment exhibited characteristic water contents and distributions of dry weight elements, which were used to calculate respective ionized concentrations. Free axoplasmic [K+] ranged from ≃155 mM in large PNS and CNS axons to ≃120-130 mM in smaller fibers. Free [Na+] was ≃15-17 mM in larger fibers compared with 20- 25 mM in smaller axons, whereas free [Cl-]was found to be 30-55 mM in all axons. Because intracellular Ca is largely bound, ionized concentrations were not estimated. However, calculations of total (free plus bound) aqueous concentrations of this element showed that axoplasm of large CNS and PNS axons contained ≃0.7 mM Ca, whereas small fibers contained 0.1-0.2 mM. Calculated ionic equilibrium potentials were as follows (in mV): in large CNS and PNS axons, E(K) = -105, E(Na) = 60, and E(Cl) = -28; in Schwann cells, E(K) = -107, E(Na) = 33, and E(Cl) = -33; and in CNS gila, E(K) -99, E(Na) = 36, and E(Cl) = -44. Calculated resting membrane potentials were as follows (in mV, including the contribution of the Na+,K+-ATPase): large axons, about -80; small axons, about -72 to -78; and CNS gila, 91. E(Cl) is more positive than resting membrane potential in PNS and CNS axons and gila, indicating active accumulation. Direct EPMA measurement of elemental concentrations and subsequent calculation of ionized fractions in axons and glia offer fundamental neurophysiological information that has been previously unattainable.

KW - Calcium

KW - Chloride

KW - Myelinated axon

KW - Neuroglia

KW - Potassium

KW - Schwann cell

KW - Sodium

UR - http://www.scopus.com/inward/record.url?scp=0030951034&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0030951034&partnerID=8YFLogxK

M3 - Article

C2 - 9109518

AN - SCOPUS:0030951034

VL - 68

SP - 1920

EP - 1928

JO - Journal of Neurochemistry

JF - Journal of Neurochemistry

SN - 0022-3042

IS - 5

ER -