Abstract
The ATP-regulated potassium (K(ATP)) channel plays an essential role in the control of insulin release from the pancreatic β-cell. In the present study we have used the patch-clamp technique to study the direct effects of α-ketoisocaproate on the K(ATP) channel in isolated patches and intact pancreatic β-cells. In excised inside-out patches, the activity of the K(ATP) channel was dose-dependently inhibited by α-ketoisocaproate, half- maximal concentration being approximately 8 mM. The blocking effect of α- ketoisocaproate was fully reversible. Stimulation of channel activity by the addition of ATP/ADP (ratio 1) did not counteract the inhibitory effect of α- ketoisocaproate. In the presence of the metabolic inhibitor sodium azide, α- ketoisocaproate was still able to inhibit single channel activity in excised patches and to block whole cell K(ATP) currents in intact cells. No effect of α-ketoisocaproate could be obtained on either the large or the small conductance Ca2+-regulated K+ channel. Enzymatic treatment of the patches with trypsin prevented the inhibitory effect of α-ketoisocaproate. Based on these observations, it is unlikely that the blocking effect of α- ketoisocaproate is due to an unspecific effect on K+ channel pores. Leucine, the precursor of α-ketoisocaproate, did not affect K(ATP) channel activity in excised patches. Our findings are compatible with the view that α- ketoisocaproate not only affects the β-cell stimulus secretion coupling by generation of ATP but also by direct inhibition of the K(ATP) channel.
| Original language | English |
|---|---|
| Pages (from-to) | 14113-14118 |
| Number of pages | 6 |
| Journal | Journal of Biological Chemistry |
| Volume | 273 |
| Issue number | 23 |
| DOIs | |
| State | Published - Jun 5 1998 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Biochemistry
Cite this
Direct inhibition of the pancreatic β-cell ATP-regulated potassium channel by α-ketoisocaproate. / Bränström, Robert; Efendić, Suad; Berggren, Per Olof; Larsson, Olof.
In: Journal of Biological Chemistry, Vol. 273, No. 23, 05.06.1998, p. 14113-14118.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Direct inhibition of the pancreatic β-cell ATP-regulated potassium channel by α-ketoisocaproate
AU - Bränström, Robert
AU - Efendić, Suad
AU - Berggren, Per Olof
AU - Larsson, Olof
PY - 1998/6/5
Y1 - 1998/6/5
N2 - The ATP-regulated potassium (K(ATP)) channel plays an essential role in the control of insulin release from the pancreatic β-cell. In the present study we have used the patch-clamp technique to study the direct effects of α-ketoisocaproate on the K(ATP) channel in isolated patches and intact pancreatic β-cells. In excised inside-out patches, the activity of the K(ATP) channel was dose-dependently inhibited by α-ketoisocaproate, half- maximal concentration being approximately 8 mM. The blocking effect of α- ketoisocaproate was fully reversible. Stimulation of channel activity by the addition of ATP/ADP (ratio 1) did not counteract the inhibitory effect of α- ketoisocaproate. In the presence of the metabolic inhibitor sodium azide, α- ketoisocaproate was still able to inhibit single channel activity in excised patches and to block whole cell K(ATP) currents in intact cells. No effect of α-ketoisocaproate could be obtained on either the large or the small conductance Ca2+-regulated K+ channel. Enzymatic treatment of the patches with trypsin prevented the inhibitory effect of α-ketoisocaproate. Based on these observations, it is unlikely that the blocking effect of α- ketoisocaproate is due to an unspecific effect on K+ channel pores. Leucine, the precursor of α-ketoisocaproate, did not affect K(ATP) channel activity in excised patches. Our findings are compatible with the view that α- ketoisocaproate not only affects the β-cell stimulus secretion coupling by generation of ATP but also by direct inhibition of the K(ATP) channel.
AB - The ATP-regulated potassium (K(ATP)) channel plays an essential role in the control of insulin release from the pancreatic β-cell. In the present study we have used the patch-clamp technique to study the direct effects of α-ketoisocaproate on the K(ATP) channel in isolated patches and intact pancreatic β-cells. In excised inside-out patches, the activity of the K(ATP) channel was dose-dependently inhibited by α-ketoisocaproate, half- maximal concentration being approximately 8 mM. The blocking effect of α- ketoisocaproate was fully reversible. Stimulation of channel activity by the addition of ATP/ADP (ratio 1) did not counteract the inhibitory effect of α- ketoisocaproate. In the presence of the metabolic inhibitor sodium azide, α- ketoisocaproate was still able to inhibit single channel activity in excised patches and to block whole cell K(ATP) currents in intact cells. No effect of α-ketoisocaproate could be obtained on either the large or the small conductance Ca2+-regulated K+ channel. Enzymatic treatment of the patches with trypsin prevented the inhibitory effect of α-ketoisocaproate. Based on these observations, it is unlikely that the blocking effect of α- ketoisocaproate is due to an unspecific effect on K+ channel pores. Leucine, the precursor of α-ketoisocaproate, did not affect K(ATP) channel activity in excised patches. Our findings are compatible with the view that α- ketoisocaproate not only affects the β-cell stimulus secretion coupling by generation of ATP but also by direct inhibition of the K(ATP) channel.
UR - http://www.scopus.com/inward/record.url?scp=0032486283&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0032486283&partnerID=8YFLogxK
U2 - 10.1074/jbc.273.23.14113
DO - 10.1074/jbc.273.23.14113
M3 - Article
C2 - 9603910
AN - SCOPUS:0032486283
VL - 273
SP - 14113
EP - 14118
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 23
ER -