Summary
The present study demonstrates the action of the hypoglycaemic drugs repaglinide and glibenclamide in cultured newborn rat islet cells and mouse ΒTC3 cells. In cell-attached membrane patches of newborn rat islet cells repaglinide (10 nmol/l) and glibenclamide (20 nmol/l) decrease the open probability of single ATP-sensitive K+-channels to approximately 10% of the activity prior to addition of the drugs in short-term experiments (<5 min). The influence of repaglinide and glibenclamide on the ATP-sensitive K+ current was studied using the whole-cell patch clamp configuration. A half-maximal steady-state inhibition of the ATP-sensitive K+ currents is observed at 89 pmol/l repaglinide and at 47 pmol/l glibenclamide in whole-cell experiments of longer duration (30 min). Applying digital Ca2+ imaging on single ΒTC3 cells we found that repaglinide and glibenclamide induced a concentration-dependent increase in intracellular free Ca2+ concentration ([Ca2+]i) with a half-maximal effect at 0.5 nmol/l for both drugs in long-term experiments (30 min). The rise in [Ca2+]i results from Ca2+ entry through voltage-dependent L-type Ca2+-channels since it is inhibited by verapamil (10 Μmol/l). The effect of repaglinide and glibenclamide is partly reversible (≈80%).
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Abbreviations
- K+ ATP-channel:
-
ATP-sensitive potassium channel
- [Ca2+]i :
-
intracellular free Ca2+ concentration
- EGTA:
-
ethylene glycol-O,O′-bis(2-aminoethyl]-N′,N,N′,N′-tetraacetic acid
- IC50 :
-
apparent inhibitor constant
- repaglinide:
-
((S)-(+)-2-ethoxy-4-[2-((3-methyl-1-[2-(1-piperidinyl) phenyl]-butyl)amino)-2-oxoethyl) benzoic acid
- NIDDM:
-
non-insulin-dependent diabetes mellitus
- ΒTC3 cells:
-
transgenic mouse insulinoma tumour cell line
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Gromada, J., Dissing, S., Kofod, H. et al. Effects of the hypoglycaemic drugs repaglinide and glibenclamide on ATP-sensitive potassium-channels and cytosolic calcium levels in Β TC3 cells and rat pancreatic beta cells. Diabetologia 38, 1025–1032 (1995). https://doi.org/10.1007/BF00402171
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DOI: https://doi.org/10.1007/BF00402171