Abstract
Increase of the glucose concentration from 3 to 11 mM resulted in a triphasic release of insulin from perifused ob/ob-mouse β-cells. A slight inhibition was followed after 2 min by a marked peak and a less pronounced sustained response. At the lower glucose concentration glycine had only marginal effects. However, in the presence of 11 mM glucose, 1-10 mM glycine triggered an immediate and dose-dependent response with an initial peak of insulin release followed by sustained stimulation. In individual β-cells, rise of the glucose concentration from 3 to 11 mM induced initial lowering of the cytoplasmic Ca2+ concentration ([Ca2+]i) followed by large amplitude oscillations from a level of 50-90 nM to peak values exceeding 300 nM. Already at a concentration of 1 mM, glycine transformed the oscillatory pattern into a sustained level with increase of time-average [Ca2+]i. This elevation became more pronounced in the presence of 10 mM glycine. The effects of glycine on insulin release and [Ca2+]i required extracellular Na+ and were reproduced with the N-methyl analogue sarcosine. It is suggested that glycine potentiation of secretion reflects the elevation of time-average [Ca2+]i both by increased entry and reduced elimination of the cation from the cytoplasm.
Original language | English |
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Pages (from-to) | 243-247 |
Number of pages | 5 |
Journal | BBA - Molecular Cell Research |
Volume | 1137 |
Issue number | 3 |
DOIs | |
Publication status | Published - 17 Nov 1992 |
Externally published | Yes |
Keywords
- Cytoplasmic calcium
- Glucose
- Glycine
- Insulin
- Oscillation
- Secretion