Cytoplasmic Ca2+ in glucagon-producing pancreatic α-cells exposed to carbachol and agents affecting Na+ fluxes

被引:0
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作者
Alf Berts
Erik Gylfe
Bo Hellman
机构
[1] Uppsala University,Department of Medical Cell Biology
来源
Endocrine | 1997年 / 6卷
关键词
α-Cell; glucagon; Ca; oscillations; Na; carbachol;
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学科分类号
摘要
The cytoplasmic Ca2+ concentration ([Ca2+]i) was measured with dual wavelength fluorometry in glucagon-producing mouse pancreatic α-cells loaded with the indicator fura-2. Spontaneous rhythmic activity in terms of slow oscillations from a basal level was observed at 3 mM glucose. Like in the insulin-secreting β-cells the generation of [Ca2+]i oscillations in the α-cells was affected by the activity of the Na/K pump. Blocking the pump with ouabain resulted in an initial rise of [Ca2+]i followed by gradual return to the basal level. The oscillations were transformed into sustained elevation of [Ca2+]i by 10 mMl-glycine, which is cotransported with Na+. A similar but less pronounced effect was obtained when Na+ was cotransported with 10 mM of the nonmetabolizable amino acid α-amino-isobutyric acid.l-glycine induced sustained increase of [Ca2+]i also when the oscillatory activity was suppressed by exposing the α-cells to 20 mM glucose in the presence of insulin. The observation that carbachol induces a [Ca2+]i response in isolated α-cells calls for reconsideration of current ideas that muscarinic stimulation of glucagon release is an indirect effect mediated by adjacent β-cells.
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页码:79 / 83
页数:4
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