Ion channels classes in purified olfactory cilia membranes: planar
lipid bilayer studies.
Jorquera, Orlando, Ramon Latorre, and Pedro Labarca.
Centro de Estudios Cientificos de Santiago, Casilla 16443, Santiago
9 and Department of Biology, Faculty of Sciences, University of
Chile, Santiago, Chile
APStracts 2:0234C, 1995.
Ciliary membrane fragment fusion to planar lipid bilayers resulted in
the insertion of four ion channel types. cAMP-activated, cation
-selective channels could be detected only in the absence of Ca2+ and
had a conductance of 23 pS. They exhibited an apparent dissociation
constant (Kd) for the cyclic nucleotide of 30 [mu]M and a PNa/PK =
2.4. The cAMP-cation selective channel co-inserted with a K+
-selective channel refractory to cAMP, Ca2+ and IP3. This K+ channel
was voltage-independent and exhibited open conductance substates of
60 and 112 pS. cAMP was found also to modulate a novel K+ channel
with a Kd = 140 [mu]M. It displayed three nearly equally spaced open
substates with conductances of 34, 80 and 130 pS. In the absence and
in the presence of cAMP the probability of occurrence of the open
substates was binomially distributed. A fourth channel type was a
Ca2+-activated K+ channel with a conductance of 240 pS. It was
blocked by charybdotoxin at nanomolar concentrations (Kd = 3 nM).
These results add support to the idea that, besides cAMP-activated
cation- selective channels, vertebrate chemosensory olfactory
membranes possess an arrangement of ion channels.
Received 23 January 1995; accepted in final form 18 May 1995.
APS Manuscript Number C42-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.