Original Publication Date
The Biophysical Journal
DOI of Original Publication
Date of Submission
Plasma insulin is pulsatile and reflects oscillatory insulin secretion from pancreatic islets. Although both islet Ca2+ and metabolism oscillate, there is disagreement over their interrelationship, and whether they can be dissociated. In some models of islet oscillations, Ca2+ must oscillate for metabolic oscillations to occur, whereas in others metabolic oscillations can occur without Ca2+ oscillations. We used NAD(P)H fluorescence to assay oscillatory metabolism in mouse islets stimulated by 11.1 mM glucose. After abolishing Ca2+ oscillations with 200 μM diazoxide, we observed that oscillations in NAD(P)H persisted in 34% of islets (n = 101). In the remainder of the islets (66%) both Ca2+ and NAD(P)H oscillations were eliminated by diazoxide. However, in most of these islets NAD(P)H oscillations could be restored and amplified by raising extracellular KCl, which elevated the intracellular Ca2+ level but did not restore Ca2+oscillations. Comparatively, we examined islets from ATP-sensitive K+ (KATP) channel-deficient SUR1−/−mice. Again NAD(P)H oscillations were evident even though Ca2+ and membrane potential oscillations were abolished. These observations are predicted by the dual oscillator model, in which intrinsic metabolic oscillations and Ca2+ feedback both contribute to the oscillatory islet behavior, but argue against other models that depend on Ca2+ oscillations for metabolic oscillations to occur.
From The Biophysical Journal, Merrins, M.J., Fendler, B., Zhang, M., et al., Metabolic Oscillations in Pancreatic Islets Depend on the Intracellular Ca2+ Level but Not Ca2+ Oscillations, Vol. 99, Page 76. Copyright © 2010 Biophysical Society. Published by Elsevier Inc. Reprinted with permission.
Is Part Of
VCU Pharmacology and Toxicology Publications