22 research outputs found
The Na+-K+-2Cl- cotransporter and the osmotic stress response in a model salt transport epithelium.
Epithelia are physiologically exposed to osmotic stress resulting in alteration
of cell volume in several aspects of their functioning; therefore, the activation
of ‘emergency’ systems of rapid cell volume regulation is fundamental in
their physiology. In this review, the physiological response to osmotic stress,
particularly hypertonic stress, was described in a salt-transporting epithelium,
the intestine of the euryhaline teleost European eel. This epithelium is
physiologically exposed to changes in extracellular osmolarity and represents
a good physiological model for functional studies on cellular volume regulation,
permitting the study of volume regulated ion transport mechanisms in
a native tissue. An absorptive form of the cotransporter, homologue of the
renal NKCC2, localized on the apical membrane, was found in the intestine
of the euryhaline teleost European eel. This cotransporter accounts for the
luminal uptake of Cl); it operates in series with a basolateral Cl) conductance
and presumably a basolateral electroneutral KCl cotransport and in
parallel with a luminal K+ conductance. The ion transport model described
for eel intestine, based on the operation of an absorptive luminal Na+–K+–
2Cl), is basically the same as the model that has been proposed for the thick
ascending limb (cTAL) of the mammalian renal cortex. This paper focuses on
the role of Na+–K+–2Cl) cotransport in the responses to hypertonic stress in
the eel intestine and the role of cytoskeleton (either actin-based or tubulin
based) is discussed