Glycine transformation of Ca2+ oscillations into a sustained increase parallels potentiation of insulin release

Anders Tengholm, Neville McClenaghan, Eva Grapengiesser, Erik Gylfe, Bo Hellman

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)

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 languageEnglish
Pages (from-to)243-247
Number of pages5
JournalBBA - Molecular Cell Research
Volume1137
Issue number3
DOIs
Publication statusPublished - 17 Nov 1992
Externally publishedYes

Keywords

  • Cytoplasmic calcium
  • Glucose
  • Glycine
  • Insulin
  • Oscillation
  • Secretion

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