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Imidazoline‐induced amplification of glucose‐ and carbachol‐stimulated insulin release includes a marked suppression of islet nitric oxide generation in the mouse
Author(s) -
MeiduteAbaraviciene S.,
Mosen H.,
Lundquist I.,
Salehi A.
Publication year - 2009
Publication title -
acta physiologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.591
H-Index - 116
eISSN - 1748-1716
pISSN - 1748-1708
DOI - 10.1111/j.1748-1716.2008.01896.x
Subject(s) - medicine , insulin , endocrinology , islet , nitric oxide synthase , nitric oxide , carbachol , imidazoline receptor , insulin oscillation , biology , chemistry , stimulation
Aim: The role of islet nitric oxide (NO) production in insulin‐releasing mechanisms is unclear. We examined whether the beneficial effects of the imidazoline derivative RX 871024 (RX) on β‐cell function might be related to perturbations of islet NO production. Methods: Experiments were performed with isolated islets or intact mice challenged with glucose or carbachol with or without RX treatment. Insulin was determined with radioimmunoassay, NO generation with high‐performance liquid chromatography and expression of inducible NO synthase (iNOS) with confocal microscopy. Results: RX treatment, in doses lacking effects on basal insulin, greatly amplified insulin release stimulated by the NO‐generating secretagogues glucose and carbachol both in vitro and in vivo . RX also improved the glucose tolerance curve. Islets incubated at high glucose levels (20 mmol L −1 ) displayed increased NO production derived from both neuronal constitutive NO synthase (ncNOS) and iNOS. RX abrogated this glucose‐induced NO production concomitant with amplification of insulin release. Confocal microscopy revealed abundant iNOS expression in β cells after incubation of islets at high but not low glucose levels. This was abolished after RX treatment. Similarly, islets cultured for 24 h at high glucose levels showed intense iNOS expression in β cells. This was abrogated with RX and followed by an amplified glucose‐induced insulin release. Conclusion: RX effectively counteracts the negative impact of β‐cell NO generation on insulin release stimulated by glucose and carbachol suggesting imidazoline compounds by virtue of NOS inhibitory properties being of potential therapeutic value for treatment of β‐cell dysfunction in hyperglycaemia and type 2 diabetes.