Stimulation of insulin release by glucose requires increased metabolism of glucose and a rise in cytosolic free Ca2+ in the pancreatic β-cell. It is accompanied by increases in respiratory rate, pyridine and flavin nucleotide reduction state, intracellular pH and the ATP/ADP ratio. To test alternative proposals of the regulatory relationships among free Ca2+, mitochondrial metabolism and cellular energy state, we determined the temporal sequence of these metabolic and ionic changes following addition of glucose to clonal pancreatic β-cells (HIT). Combined measurements of the native fluorescence of reduced pyridine nucleotides and oxidized flavin, intracellular pH, and free Ca2+ were performed together with simultaneous measurement of O2 tension or removal of samples for assay of the ATP/ADP ratio. The initial changes were detected in three phases. First, decreases occurred in the ATP/ADP ratio (< 3 s) and increases in pyridine (2±1 s) and flavin (2±1 s) nucleotide reduction. Next, increases in the O2 consumption rate (20±5 s), the ATP/ADP ratio (29±12 s) and internal pH (48±5 s) were observed. Finally, cytosolic free Ca2+ rose (114±10 s). Maximal changes in the ATP/ADP ratio, O2 consumption and pyridine and flavin nucleotide fluorescence preceded the beginning of the Ca2+ change. These relationships are consistent with a model in which phosphorylation of glucose is the initial event which generates the signals that lead to an increase in respiration, a rise in the ATP/ADP ratio and finally influx of Ca2+. Our results indicate that Ca2+ does not function as the initiator of increased mitochondrial respiration.
Skip Nav Destination
Article navigation
Research Article|
May 01 1996
Temporal sequence of metabolic and ionic events in glucose-stimulated clonal pancreatic β-cells (HIT)
Vildan N. CIVELEK;
Vildan N. CIVELEK
*Diabetes and Metabolism Unit, Evans Department of Medicine, U.S.A.
Search for other works by this author on:
Jude T. DEENEY;
Jude T. DEENEY
*Diabetes and Metabolism Unit, Evans Department of Medicine, U.S.A.
Search for other works by this author on:
Kari KUBIK;
Kari KUBIK
*Diabetes and Metabolism Unit, Evans Department of Medicine, U.S.A.
Search for other works by this author on:
Vera SCHULTZ;
Vera SCHULTZ
†Department of Biochemistry, Boston University Medical Center, Boston, MA 02118, U.S.A.
Search for other works by this author on:
Keith TORNHEIM;
Keith TORNHEIM
*Diabetes and Metabolism Unit, Evans Department of Medicine, U.S.A.
†Department of Biochemistry, Boston University Medical Center, Boston, MA 02118, U.S.A.
Search for other works by this author on:
Barbara E. CORKEY
Barbara E. CORKEY
‡
*Diabetes and Metabolism Unit, Evans Department of Medicine, U.S.A.
†Department of Biochemistry, Boston University Medical Center, Boston, MA 02118, U.S.A.
‡To whom correspondence should be addressed.
Search for other works by this author on:
Publisher: Portland Press Ltd
Received:
September 07 1995
Revision Received:
December 11 1995
Accepted:
December 20 1995
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1996
1996
Biochem J (1996) 315 (3): 1015–1019.
Article history
Received:
September 07 1995
Revision Received:
December 11 1995
Accepted:
December 20 1995
Citation
Vildan N. CIVELEK, Jude T. DEENEY, Kari KUBIK, Vera SCHULTZ, Keith TORNHEIM, Barbara E. CORKEY; Temporal sequence of metabolic and ionic events in glucose-stimulated clonal pancreatic β-cells (HIT). Biochem J 1 May 1996; 315 (3): 1015–1019. doi: https://doi.org/10.1042/bj3151015
Download citation file:
Sign in
Don't already have an account? Register
Sign in to your personal account
You could not be signed in. Please check your email address / username and password and try again.
Captcha Validation Error. Please try again.