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Albert Salehi

S Albert Salehi

Research team manager

Albert Salehi

Carbon monoxide stimulates insulin release and propagates Ca2+ signals between pancreatic beta-cells

Author

  • Ingmar Lundquist
  • Per Alm
  • S Albert Salehi
  • Ragnar Henningsson
  • E Grapengiesser
  • B Hellman

Summary, in English

A key question for understanding the mechanisms of pulsatile insulin release is how the underlying beta-cell oscillations of the cytoplasmic Ca2+ concentration ([Ca2+](i)) are synchronized within and among the islets in the pancreas. Nitric oxide has been proposed to coordinate the activity of the beta-cells by precipitating transients of [Ca2+](i). Comparing ob/ob mice and lean controls, we have now studied the action of carbon monoxide (CO), another neurotransmitter with stimulatory effects on cGMP production. A strong immunoreactivity for the CO-producing constitutive heme oxygenase (HO-2) was found in ganglionic cells located in the periphery of the islets and in almost all islet endocrine cells. Islets from ob/ob mice had sixfold higher generation of CO ( 1 nmol.min(-1).mg protein(-1)) than the lean controls. This is 100-fold the rate for their constitutive production of NO. Moreover, islets from ob/ob mice showed a threefold increase in HO-2 expression and expressed inducible HO (HO-1). The presence of an excessive islet production of CO in the ob/ob mouse had its counterpart in a pronounced suppression of the glucose-stimulated insulin release from islets exposed to the HO inhibitor Zn-protoporhyrin (10 muM) and in a 16 times higher frequency of [Ca2+](i) transients in their beta-cells. Hemin (0.1 and 1.0 muM), the natural substrate for HO, promoted the appearance of [Ca2+](i) transients, and 10 muM of the HO inhibitors Zn-protoporphyrin and Cr-mesoporphyrin had a suppressive action both on the firing of transients and their synchronization. It is concluded that the increased islet production of CO contributes to the hyperinsulinemia in ob/ob mice. In addition to serving as a positive modulator of glucose-stimulated insulin release, CO acts as a messenger propagating Ca2+ signals with coordinating effects on the beta-cell rhythmicity.

Department/s

  • Islet cell physiology
  • Division of Medical Microbiology
  • Department of Experimental Medical Science

Publishing year

2003

Language

English

Pages

1055-1063

Publication/Series

American Journal of Physiology: Endocrinology and Metabolism

Volume

285

Issue

5

Document type

Journal article

Publisher

American Physiological Society

Topic

  • Physiology

Keywords

  • calcium ion
  • carbon monoxide

Status

Published

Research group

  • Islet cell physiology

ISBN/ISSN/Other

  • ISSN: 1522-1555