Swelling-activated k+ transport via two functionally distinct
pathways in eel erythrocytes.
Bursell, James D. H., Kiaran Kirk.
University Laboratory of Physiology, Parks Rd, Oxford OX1 3PT
APStracts 2:0191R, 1995.
Following osmotic swelling, erythrocytes from the European eel,
Anguilla anguilla, underwent a regulatory volume decrease. This was
prevented by replacement of Na+ with K+ in the suspending medium,
consistent with a role for the (normally outward) electrochemical K+
gradient in the volume-regulatory response. The effect of cell
swelling on K+ transport in these cells was investigated using 86Rb+
as a tracer for K+. Osmotic swelling resulted in an increase in
ouabain-insensitive K+ transport that was highest for cells in Cl-
and Br- media but which was also significant in I- and NO3- media.
Treatment of eel erythrocytes suspended in isotonic Cl- or Br- (but
not I- or NO3-) media with the sulfhydryl reagent N-ethylmaleimide
(NEM) resulted in a large increase in K+ transport. A quantitative
comparison of the pharmacological properties of the 'Cl--dependent'
NEM-activated pathway with those of the 'Cl--independent' pathway
mediating swelling-activated K+ transport in cells in Cl--free (NO3-
-containing) media showed there to be significant differences between
them. By contrast, the pharmacological properties of the Cl-
-independent swelling-activated K+ pathway were indistinguishable from
those of the pathway responsible for the swelling-activated transport
of taurine, the major organic osmolyte in these cells. A
pharmacological analysis of ouabain-insensitive K+ transport in cells
swollen in a hypotonic Cl--containing medium showed there to be two
components, one with the characteristics of the NEM-activated system,
the other showing the characteristics of the Cl--independent,
swelling-activated pathway. The data are consistent with the presence
of two functionally distinct swelling-activated K+ transport
mechanisms in eel erythrocytes: a KCl cotransporter that is activated
under isotonic conditions by NEM and a ('Cl--independent'), broad
-specificity channel that accommodates a diverse range of organic and
inorganic solutes.
Received 3 April 1995; accepted in final form 6 July 1995.
APS Manuscript Number R219-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.