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Albert Salehi

S Albert Salehi

Research team manager

Albert Salehi

Insulin release transduction mechanism through acid glucan 1,4-alpha-glucosidase activation is Ca2+ regulated

Author

  • S Albert Salehi
  • Henrik Mosén
  • Ingmar Lundquist

Summary, in English

An important signal involved in glucose-stimulated insulin secretion is transduced through the action of a lysosomal acid, glucan 1,4-alpha-glucosidase. We investigated the Ca2+ dependency of this enzyme activity in relation to insulin release. In isolated islets, increased levels of extracellular Ca2+ induced a large increase in acid glucan 1,4-alpha-glucosidase activity accompanied by a similar increase in insulin release at both substimulatory and stimulatory concentrations of glucose. At low glucose the Ca2+ "inflow" blocker nifedipine unexpectedly stimulated enzyme activity without affecting insulin release. However, nifedipine suppressed 45Ca2+ outflow from perifused islets at low glucose and at Ca2+ deficiency when intracellular Ca2+ was mobilized by carbachol. This nifedipine-induced retention of Ca2+ was reflected in increased acid glucan 1,4-alpha-glucosidase activity. Adding different physiological Ca2+ concentrations or nifedipine to islet homogenates did not increase enzyme activity. Neither selective glucan 1,4-alpha-glucosidase inhibition nor the ensuing suppression of glucose-induced insulin release was overcome by a maximal Ca2+ concentration. Hence, Ca(2+)-induced changes in acid glucan 1,4-alpha-glucosidase activity were intimately coupled to similar changes in Ca(2+)-glucose-induced insulin release. Ca2+ did not affect the enzyme itself but presumably activated either glucan 1,4-alpha-glucosidase-containing organelles or closely interconnected messengers.

Department/s

  • Islet cell physiology
  • Clinical Physiology (Lund)

Publishing year

1998

Language

English

Pages

459-468

Publication/Series

American Journal of Physiology - Endocrinology and Metabolism

Volume

274

Issue

3

Document type

Journal article

Publisher

American Physiological Society

Topic

  • Cardiac and Cardiovascular Systems
  • Endocrinology and Diabetes
  • Respiratory Medicine and Allergy

Keywords

  • carbachol
  • emiglitate
  • calcium ion
  • nifedipine
  • pancreatic islets
  • lysosomal enzymes

Status

Published

Research group

  • Islet cell physiology

ISBN/ISSN/Other

  • ISSN: 1522-1555