Glucose triggers protein kinase A-dependent insulin secretion in mouse pancreatic islets through activation of the K+ATP channel-dependent pathway

Eur J Endocrinol. 2005 Apr;152(4):671-7. doi: 10.1530/eje.1.01885.

Abstract

Objective: To assess the significance of protein kinase A (PKA) in glucose triggering of ATP-sensitive K(+) (K(+)(ATP)) channel-dependent insulin secretion and in glucose amplification of K(+)(ATP) channel-independent insulin secretion.

Methods: Insulin release from cultured perifused mouse pancreatic islets was determined by radioimmunoassay.

Results: In islets cultured at 5.5 mmol/l glucose, and then perifused in physiological Krebs-Ringer medium, the PKA inhibitors, H89 (10 micromol/l) and PKI 6-22 amide (30 micromol/l) did not inhibit glucose (16.7 mmol/l)-induced insulin secretion, but inhibited stimulation by the adenylyl cyclase activator, forskolin (10 micromol/l). In the presence of 60 mmol/l K(+) and 250 micromol/l diazoxide, which stimulates maximum Ca(2+) influx independently of K(+)(ATP) channels, H89 (10 micromol/l) inhibited Ca(2+)-evoked insulin secretion, but failed to prevent glucose amplification of K(+)(ATP) channel-independent insulin secretion. In the presence of 1 mmol/l ouabain and 250 micromol/l diazoxide, which cause modest Ca(2+) influx, glucose amplification of K(+)(ATP) channel-independent insulin secretion was observed without concomitant Ca(2+) stimulation of PKA activity. In islets cultured at 16.7 mmol/l glucose, glucose (16.7 mmol/l)-induced insulin secretion in physiological Krebs-Ringer medium was augmented and now inhibited by H89 (10 micromol/l), implicating that culture at 16.7 mmol/l glucose may increase Ca(2+)-sensitive adenylyl cyclase activity and hence PKA activity. In accordance, Ca(2+)-evoked insulin secretion at 60 mmol/l K(+) and 250 micromol/l diazoxide was improved, whereas glucose amplification of K(+)(ATP) channel-independent insulin secretion was unaffected.

Conclusions: Glucose may activate PKA through triggering of the K(+)(ATP) channel-dependent pathway. Glucose amplification of K(+)(ATP) channel-independent insulin secretion, on the other hand, occurs by PKA-independent mechanisms.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / pharmacology*
  • Adenylyl Cyclases / metabolism
  • Animals
  • Calcium / metabolism
  • Calcium / pharmacology
  • Cells, Cultured
  • Colforsin / pharmacology
  • Cyclic AMP / physiology
  • Cyclic AMP-Dependent Protein Kinases / antagonists & inhibitors
  • Cyclic AMP-Dependent Protein Kinases / physiology*
  • Diazoxide / pharmacology
  • Enzyme Activation / drug effects
  • Glucose / pharmacology*
  • Insulin / metabolism*
  • Insulin Secretion
  • Intracellular Signaling Peptides and Proteins / pharmacology
  • Islets of Langerhans / drug effects
  • Islets of Langerhans / metabolism*
  • Isoquinolines / pharmacology
  • Male
  • Mice
  • Ouabain / pharmacology
  • Potassium / pharmacology
  • Potassium Channels / physiology*
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / physiology
  • Sulfonamides / pharmacology

Substances

  • Insulin
  • Intracellular Signaling Peptides and Proteins
  • Isoquinolines
  • Potassium Channels
  • Sulfonamides
  • protein kinase modulator
  • Colforsin
  • Ouabain
  • Adenosine Triphosphate
  • Cyclic AMP
  • Cyclic AMP-Dependent Protein Kinases
  • Protein Kinase C
  • Adenylyl Cyclases
  • Glucose
  • N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide
  • Diazoxide
  • Potassium
  • Calcium