AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 3 590-R597, Copyright © 1995 by American Physiological Society
Regulatory volume decrease in lamprey erythrocytes: mechanisms of K+ and Cl- loss
L. V. Virkki and M. Nikinmaa
Department of Biosciences, FIN-00014 University of Helsinki, Finland.
The nature of the swelling-activated K+ and Cl- transport pathways of
lamprey (Lampetra fluviatilis) erythrocytes was studied. In isosmotic
medium, unidirectional K+ and Cl- effluxes appear to be largely mediated by
conductive pathways. Unidirectional Cl- efflux increased as a function of a
decrease in medium osmolarity. The swelling-activated Cl- transport was
inhibited by
R(+)-[(2-n-butyl-6,7-dichloro-2-cyclopentyl-2,3-dihydro-1-oxo-1H-inde n-5-
yl)oxy]acetic acid (DIOA), furosemide, and
4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). In contrast,
moderate cell swelling did not increase unidirectional ouabain-insensitive
K+ efflux. However, inhibition of transport by Ba2+ was markedly reduced.
This suggests that the Ba(2+)-sensitive pathway that mediated most of the
K+ efflux in isosmotic conditions was inhibited by cell swelling and a
Ba(2+)-insensitive pathway was activated. DIOA had no effect on K+ efflux
in isosmotic or hyposmotic medium. These data and the finding that
substitution of NO3- or SCN- for Cl- had only a minor effect on the
swelling-induced net extrusion of K+ and water indicate that the pathways
for K+ and Cl-, activated by cell swelling, are conductive.
