Tissue and Cell 39 (2007) 195–201
Localization and irregular distribution of Na,K-ATPase
in myelin sheath from rat sciatic nerve
Sandra Alberti
a,∗
, Elisa Aparecida Greg
´
orio
b
,
C
´
esar Tadeu Spadella
a
, Constantin Cojocel
c
a
Department of Surgery, Medical School, S˜ao Paulo State University, Botucatu, S˜ao Paulo, Brazil
b
Department of Morphology, Biosciences Institute, Botucatu, S˜ao Paulo, Brazil
c
Department of Pharmacology and Toxicology, Medical School, Kuwait University, Kuwait City, Kuwait
Received 9 August 2006; received in revised form 25 March 2007; accepted 29 March 2007
Available online 15 May 2007
Abstract
Sodium, potassium adenosine triphosphatase (Na,K-ATPase) is a membrane-bound enzyme that maintains the Na
+
and K
+
gradients
used in the nervous system for generation and transmission of bioelectricity. Recently, its activity has also been demonstrated dur-
ing nerve regeneration. The present study was undertaken to investigate the ultrastructural localization and distribution of Na,K-ATPase
in peripheral nerve fibers. Small blocks of the sciatic nerves of male Wistar rats weighing 250–300 g were excised, divided into two
groups, and incubated with and without substrate, the para-nitrophenyl phosphate (pNPP). The material was processed for transmission
electron microscopy, and the ultra-thin sections were examined in a Philips CM 100
TM
electron microscope. The deposits of reac-
tion product were localized mainly on the axolemma, on axoplasmic profiles, and irregularly dispersed on the myelin sheath, but not
in the unmyelinated axons. In the axonal membrane, the precipitates were regularly distributed on the cytoplasmic side. These results
together with published data warrant further studies for the diagnosis and treatment of neuropathies with compromised Na,K-ATPase
activity.
© 2007 Elsevier Ltd. All rights reserved.
Keywords: Na,K-ATPase; Rat sciatic nerve; K-pNPPase; Myelin sheath
1. Introduction
Sodium, potassium adenosine triphosphatase (Na,K-
ATPase) is an enzyme lodged in the plasma membrane
that couples the energy derived from the hydrolysis of ATP
molecules with the translocation of Na
+
and K
+
across cell
boundaries (Skou, 1957, 1990; Koester and Siegelbaum,
2000). This active ion pumping driven by Na,K-ATPase,
also called Na,K-pump, is not merely a compensation for
the dissipation of ionic gradients, but also has a key func-
tion in both cell metabolism and neuronal excitability (Skou
and Esmann, 1992). Its functional significance in relation
∗
Corresponding author at: Dr. Al
´
ıpio dos Santos 1-32, CEP: 17012-530,
Bauru-SP, Brazil.
E-mail address: sedalberti@yahoo.com.br (S. Alberti).
to generation and transmission of bioelectricity is essen-
tial, because changes in these resting potentials can amount
to voltage pulses, with effects that depend on the type of
cell involved (Hodgkin, 1964; Urone, 1986; Chiu, 1993).
Furthermore, Na,K-ATPase is very important in other pro-
cesses, such as the exchange of substances between the cell
and its surroundings, cell volume regulation, transepithelial
transport (Ernst, 1972; Skou and Esmann, 1992; Thomas et
al., 1993; Schwartz and Westbrook, 2000). More recently,
its activity has been demonstrated during nerve regenera-
tion (Kawai et al., 1997; Liu et al., 2002; Arteaga et al.,
2004).
Na,K-ATPase is a complex of two polypeptides, alpha
and beta, and a large number of aggregated lipids (Beguin
et al., 1998). The alpha subunit contains the catalytic site for
phosphorylation and serves as the cellular receptor for car-
0040-8166/$ – see front matter © 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tice.2007.03.004