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Interference of H 2 O 2 with stimulus‐secretion coupling in mouse pancreatic β‐cells
Author(s) -
KrippeitDrews Peter,
Krämer Claudia,
Welker Susanne,
Lang Florian,
Ammon Hermann P. T.,
Drews Gisela
Publication year - 1999
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1999.471ae.x
Subject(s) - tolbutamide , intracellular , hyperpolarization (physics) , exocytosis , biophysics , membrane potential , secretion , medicine , ouabain , chemistry , endocrinology , pancreatic islets , insulin , biology , biochemistry , islet , sodium , organic chemistry , nuclear magnetic resonance spectroscopy
1 We have reported previously that in mouse pancreatic β‐cells H 2 O 2 hyperpolarizes the membrane and increases the ATP‐sensitive K + current recorded in the perforated patch configuration of the patch‐clamp technique. The present study was undertaken to elucidate the underlying mechanisms. 2 The intracellular ATP concentration measured by chemoluminescence was reduced by H 2 O 2 . The ADP concentration increased in parallel during the first 10 min, resulting in a pronounced decrease in the ATP/ADP ratio. 3 Consistent with these results, glucose‐stimulated insulin secretion from isolated islets was inhibited by H 2 O 2 . 4 Membrane hyperpolarization measured with intracellular microelectrodes in intact islets and inhibition of insulin secretion were counteracted by tolbutamide, indicating that the channels are still responsive to inhibitors and that the ATP concentration is not too low to trigger exocytosis. However, the sensitivity of the β‐cells to tolbutamide was reduced after treatment with H 2 O 2 . 5 H 2 O 2 increased the intracellular Ca 2+ activity ([Ca 2+ ] i ) in a biphasic manner. A first transient rise in [Ca 2+ ] i due to mobilization of Ca 2+ from intracellular stores was followed by a sustained increase, which was at least partly dependent on Ca 2+ influx. The first phase seems to reflect Ca 2+ mobilization from mitochondria. 6 Our results demonstrate that H 2 O 2 interferes with glucose metabolism, which influences the membrane potential and ATP‐sensitive K + current via the intracellular concentration of ATP. These events finally lead to an inhibition of insulin secretion despite an increase in [Ca 2+ ] i .