K+ transport in Malpighian tubules of Tenebrio molitor L.: is a KATP channel involved?
U. I. M. Wiehart1,
G. Klein2,
P. Steels2,
S. W. Nicolson1 and
E. Van Kerkhove2,*
1 Department of Zoology and Entomology, University of Pretoria, Pretoria
0002, South Africa
2 Laboratory of Physiology, Biomed CMK, Limburgs Universitair Centrum, B3590
Diepenbeek, Belgium
View larger version (14K):
[in a new window]
|
Fig. 1. Effect of glibenclamide on fluid secretion by tubules of Tenebrio.
Glibenclamide was tested at 0.1 mmol l-1 (triangles) and 0.5 mmol
l-1 (circles) in control Ringer (50 mmol l-1
K+). Secretion rates recovered after stimulation with
Tenmo-DH37 (100 nmol l-1). The horizontal bars indicate
the time of exposure to glibenclamide (broken bar) and to
Tenmo-DH37 (solid bar). Data are presented as means ± 1
S.E.M. for 7-8 tubules.
|
|
View larger version (10K):
[in a new window]
|
Fig. 2. Response of basolateral membrane potential (Vbl) to
glibenclamide (Glib.). In a low [K+] bath (5 mmol l-1
K+) Vbl responded to glibenclamide by either
(A) a small but significant hyperpolarization of 3.6±1.2 mV
(P=0.01, n=8) or (B) a significant depolarization of
9±1.5 mV (P=0.008, n=4). Addition of 6 mmol
l-1 Ba2+ reinforced the initial response of
glibenclamide.
|
|
View larger version (12K):
[in a new window]
|
Fig. 3. (A) Effect of ouabain on basolateral membrane potential
(Vbl) in low bath [K+] (5 mmol l-1)
measured in the presence of Ba2+. (B) Summary of the response of
Vbl to ouabain. Data are presented as means ± 1
S.E.M. (n=16, P<0.001).
|
|
View larger version (13K):
[in a new window]
|
Fig. 4. Typical experiments showing the effect of ouabain on basolateral membrane
potential (Vbl) in the presence of glibenclamide (Glib.)
and Ba2+. The hyperpolarization (A) or depolarization (B) of
glibenclamide and Ba2+ is followed by a depolarization of
Vbl with the addition of 1 mmol l-1 ouabain.
The experiments were carried out in low bath [K+] (5 mmol
l-1).
|
|
View larger version (15K):
[in a new window]
|
Fig. 5. (A) Response of basolateral membrane potential (Vbl) to
different bathing K+ concentrations in the presence of
Ba2+. The depolarization of Vbl when changing
the [K+] from 5 mmol l-1 to 140 mmol l-1 is
followed by a repolarization after 3-8 min. (B) Summary of the effect of
Ba2+ in various [K+]. Data are presented as means
± 1 S.E.M. (n=6).
|
|
View larger version (8K):
[in a new window]
|
Fig. 6. Slow response of basolateral membrane potential (Vbl)
to different bathing K+ concentrations in the presence of
glibenclamide (Glib.) and Ba2+. The depolarization of
Vbl when changing the [K+] from 5 mmol
l-1 to 140 mmol l-1 is no longer followed by a
repolarization (n=6).
|
|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati 
Twitter What's this?
© The Company of Biologists Ltd 2003
