ATP is released from pancreatic acini in response to cholinergic and hormonal stimulation. The same stimuli cause exocytosis of ZG (zymogen granules) and release of digestive enzymes. The aim of the present study was to determine whether ZG stored ATP and to characterize the uptake mechanism for ATP transport into the ZG. ZG were isolated and the ATP content was measured using luciferin/luciferase assays and was related to protein in the sample. The estimate of ATP concentration in freshly isolated granules was 40–120 μM. The ATP uptake had an apparent Km value of 4.9±2.1 mM when granules were incubated without Mg2+ and a Km value of 0.47±0.05 mM in the presence of Mg2+, both in pH 6.0 buffers. The uptake of ATP was significantly higher at pH 7.2 compared with pH 6.0 solutions. The anion transport blockers DIDS (4,4′-di-isothiocyanostilbene-2,2′-disulfonate) and Evans Blue inhibited ATP transport. Western blot analysis on the ZG showed the presence of VNUT (vesicular nucleotide transporter). Together, these findings indicate that VNUT may be responsible for the ATP uptake into ZG. Furthermore, the present study shows the presence of ATP together with digestive enzymes in ZG. This indicates that co-released ATP would regulate P2 receptors in pancreatic ducts and, thus, ductal secretion, and this would aid delivery of enzymes to the duodenum.
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Research Article|
June 28 2010
ATP storage and uptake by isolated pancreatic zymogen granules
Kristian A. Haanes;
Kristian A. Haanes
1Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen, Denmark
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Ivana Novak
Ivana Novak
1
1Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen, Denmark
1To whom correspondence should be addressed (email inovak@bio.ku.dk).
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Publisher: Portland Press Ltd
Received:
August 26 2009
Revision Received:
April 23 2010
Accepted:
May 04 2010
Accepted Manuscript online:
May 04 2010
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© The Authors Journal compilation © 2010 Biochemical Society
2010
Biochem J (2010) 429 (2): 303–311.
Article history
Received:
August 26 2009
Revision Received:
April 23 2010
Accepted:
May 04 2010
Accepted Manuscript online:
May 04 2010
Citation
Kristian A. Haanes, Ivana Novak; ATP storage and uptake by isolated pancreatic zymogen granules. Biochem J 15 July 2010; 429 (2): 303–311. doi: https://doi.org/10.1042/BJ20091337
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