Inhibition of p-chloromercuribenzoate- and glucose-induced insulin release in vitro by methylene blue, diamide, and tert-butyl hydroperoxide
Ammon, H.P.; Akhtar, M.S.; Niklas, H.; Hegner, D.
Molecular Pharmacology 13(4): 598-605
1977
ISSN/ISBN: 0026-895X PMID: 329119 Document Number: 113143
This investigation was designed to explore the possible role of NADPH and reduced glutathione in insulin secretion and their relationship to thiol groups located in the .beta.-cell membrane. The effects of 2 .mu.g/ml of methylene blue (an oxidant of NADPH), 0.1 mM diamide (an oxidant of GSH) and 2 mM tert-butyl hydroperoxide (a substrate of GSH peroxidase) were studied on release of insulin from isolated, perfused rat pancreas and pancreatic islets. p-Chloromercuribenzoate (a thiol reagent triggering insulin release supposedly by virtue of its action on superficial thiol groups in .beta.-cell membranes) was used at 0.1 mM to initiate insulin secretion from isolated, perfused rat pancreas, while isolated islets were stimulated to release insulin with 3 mg/ml of glucose. Both phases of p-chloromercuribenzoate-triggered insulin release were significantly suppressed by methylene blue, diamide and tert-butyl hydroperoxide. These substances inhibited glucose-stimulated insulin release from isolated islets. Apparently stimulation of insulin release by p-chloromercuribenzoate and glucose depends on the content of NADPH and GSH in the islets. Thiol groups in the .beta.-cell membrane, which are thought to be related to insulin release, possibly are kept in the reduced state.