ATP storage and uptake in isolated pancreatic zymogen granules

TY - ABST

T1 - ATP storage and uptake in isolated pancreatic zymogen granules

AU - Haanes, Kristian Agmund

AU - Novak, Ivana

N1 - Udgivelsesdato: June, 2010 Volumne: 6

PY - 2010/7/15

Y1 - 2010/7/15

N2 - 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′-diisothiocyanostilbene- 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.

AB - 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′-diisothiocyanostilbene- 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.

U2 - 10.1007/s11302-010-9187-6

DO - 10.1007/s11302-010-9187-6

M3 - Conference abstract in journal

SN - 1573-9538

SP - 12

JO - Purinergic Signalling

JF - Purinergic Signalling

IS - Suppl. 1

T2 - Purines 2010: Adenine Nucleosides and Nucleotides in Biomedicine

Y2 - 30 May 2010 through 2 June 2010

ER -