PMID- 2451014
OWN - NLM
STAT- MEDLINE
DCOM- 19880512
LR  - 20200304
IS  - 0022-3751 (Print)
IS  - 1469-7793 (Electronic)
IS  - 0022-3751 (Linking)
VI  - 391
DP  - 1987 Oct
TI  - The effects of magnesium upon adenosine triphosphate-sensitive potassium channels 
      in a rat insulin-secreting cell line.
PG  - 611-29
AB  - 1. The patch-clamp method of single-channel recording was applied to K+ channels 
      which are inhibited by intracellular adenosine 5'-triphosphate (ATP: K+-ATP 
      channels) in membrane patches obtained from the insulin-secreting cloned cell 
      line RINm5F. 2. The magnitude of K+ currents flowing outwards through these 
      K+-ATP channels was reduced by internal Mg2+ ions in a dose-dependent manner. 
      Currents flowing inwards through the channels were not affected by Mg2+. Internal 
      Na+ ions had similar effects. 3. Divalent cations (Mg2+, Sr2+ and Ca2+) applied 
      to the internal surface of the patch membrane inhibited the opening of K+-ATP 
      channels in a dose-dependent manner. Internal Na+ ions had no effect. 4. K+-ATP 
      channel activity was stimulated by adenosine 5'-diphosphate (ADP), guanosine 
      5'-triphosphate (GTP), guanosine 5'-diphosphate (GDP), guanosine 
      5'-o-(3-thiotriphosphate) (GTP gamma S) and guanosine 5'-o-(2-thiodiphosphate) 
      (GDP beta S) when millimolar Mg2+ bathed the internal surface of the patch 
      membrane. In the virtual absence of internal Mg2+ ions ADP, GTP, and GTP gamma S 
      inhibited K+-ATP channels and GDP and GDP beta S were without effect. Adenosine 
      5'-o-(2-thiodiphosphate) (ADP beta S) inhibited K+-ATP channel activity in the 
      presence and absence of Mg2+. 5. K+-ATP channel openings could be evoked by 
      either ADP or GDP in the presence of an inhibitory concentration of ATP. These 
      openings were abolished in the absence of internal Mg2+. 6. Run-down K+-ATP 
      channels could be reactivated by ATP in the presence of internal Mg2+, but not in 
      its absence. Analogues of ATP were unable to reactivate K+-ATP channels even in 
      the presence of Mg2+. 7. It is concluded that internal Mg2+ ions (i) cause the 
      rectification of the K+-ATP channel current-voltage relationship, (ii) are 
      required for K+-ATP channel activity to be maintained by a phosphorylation 
      process and (iii) are required for K+-ATP channel activity evoked by ADP, GTP and 
      GDP.
FAU - Findlay, I
AU  - Findlay I
AD  - MRC Secretory Control Research Group, University of Liverpool.
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - England
TA  - J Physiol
JT  - The Journal of physiology
JID - 0266262
RN  - 0 (Insulin)
RN  - 0 (Ion Channels)
RN  - 0 (Nucleotides)
RN  - 8L70Q75FXE (Adenosine Triphosphate)
RN  - I38ZP9992A (Magnesium)
RN  - RWP5GA015D (Potassium)
SB  - IM
MH  - Action Potentials/drug effects
MH  - Adenosine Triphosphate/*pharmacology
MH  - Animals
MH  - Cell Line
MH  - Depression, Chemical
MH  - Insulin/*metabolism
MH  - Insulin Secretion
MH  - Ion Channels/*drug effects
MH  - Magnesium/*pharmacology
MH  - Nucleotides/pharmacology
MH  - Potassium/*physiology
PMC - PMC1192235
EDAT- 1987/10/01 00:00
MHDA- 1987/10/01 00:01
PMCR- 1987/10/01
CRDT- 1987/10/01 00:00
PHST- 1987/10/01 00:00 [pubmed]
PHST- 1987/10/01 00:01 [medline]
PHST- 1987/10/01 00:00 [entrez]
PHST- 1987/10/01 00:00 [pmc-release]
AID - 10.1113/jphysiol.1987.sp016759 [doi]
PST - ppublish
SO  - J Physiol. 1987 Oct;391:611-29. doi: 10.1113/jphysiol.1987.sp016759.