Tolbutamide stimulates exocytosis of glucagon by inhibition of a mitochondrial-like ATP-sensitive K+ (KATP) conductance in rat pancreatic A-cells
(2000) In Journal of Physiology 527(1). p.109-120- Abstract
- 1. Capacitance measurements were used to examine the effects of the sulphonylurea tolbutamide on Ca2+-dependent exocytosis in isolated glucagon-secreting rat pancreatic A-cells. 2. When applied extracellularly, tolbutamide stimulated depolarization-evoked exocytosis 4.2-fold without affecting the whole-cell Ca2+ current. The concentration dependence of the stimulatory action was determined by intracellular application through the recording pipette. Tolbutamide produced a concentration-dependent increase in cell capacitance. Half-maximal stimulation was observed at 33 microM and the maximum stimulation corresponded to a 3.4-fold enhancement of exocytosis. 3. The stimulatory action of tolbutamide was dependent on protein kinase C activity.... (More)
- 1. Capacitance measurements were used to examine the effects of the sulphonylurea tolbutamide on Ca2+-dependent exocytosis in isolated glucagon-secreting rat pancreatic A-cells. 2. When applied extracellularly, tolbutamide stimulated depolarization-evoked exocytosis 4.2-fold without affecting the whole-cell Ca2+ current. The concentration dependence of the stimulatory action was determined by intracellular application through the recording pipette. Tolbutamide produced a concentration-dependent increase in cell capacitance. Half-maximal stimulation was observed at 33 microM and the maximum stimulation corresponded to a 3.4-fold enhancement of exocytosis. 3. The stimulatory action of tolbutamide was dependent on protein kinase C activity. The action of tolbutamide was mimicked by the general K+ channel blockers TEA (10 mM) and quinine (10 microM). A similar stimulation was elicited by 5-hydroxydecanoate (5-HD; 10 microM), an inhibitor of mitochondrial ATP-sensitive K+ (KATP) channels. 4. Tolbutamide-stimulated, but not TEA-induced, exocytosis was antagonized by the K+ channel openers diazoxide, pinacidil and cromakalim. 5. Dissipating the transgranular K+ gradient with nigericin and valinomycin inhibited tolbutamide- and Ca2+-evoked exocytosis. Furthermore, tolbutamide- and Ca2+-induced exocytosis were abolished by the H+ ionophore FCCP or by arresting the vacuolar (V-type) H+-ATPase with bafilomycin A1 or DCCD. Finally, ammonium chloride stimulated exocytosis to a similar extent to that obtained with tolbutamide. 6. We propose that during granular maturation, a granular V-type H+-ATPase pumps H+ into the secretory granule leading to the generation of a pH gradient across the granular membrane and the development of a positive voltage inside the granules. The pumping of H+ is facilitated by the concomitant exit of K+ through granular K+ channels with pharmacological properties similar to those of mitochondrial KATP channels. Release of granules that have been primed is then facilitated by the addition of K+ channel blockers. The resulting increase in membrane potential promotes exocytosis by unknown mechanisms, possibly involving granular alkalinization. (Less)
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https://lup.lub.lu.se/record/1117046
- author
- Hoy, M ; Olsen, H L ; Bokvist, K ; Buschard, K ; Barg, Sebastian LU ; Rorsman, Patrik LU and Gromada, J
- organization
- publishing date
- 2000
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Journal of Physiology
- volume
- 527
- issue
- 1
- pages
- 109 - 120
- publisher
- The Physiological Society
- external identifiers
-
- pmid:10944174
- scopus:0033837052
- ISSN
- 1469-7793
- language
- English
- LU publication?
- yes
- id
- 8d3a013d-b163-4d8e-812e-a880c28dcb5e (old id 1117046)
- alternative location
- http://jp.physoc.org/cgi/content/full/527/1/109
- date added to LUP
- 2016-04-01 15:44:06
- date last changed
- 2022-01-28 06:49:26
@article{8d3a013d-b163-4d8e-812e-a880c28dcb5e,
abstract = {{1. Capacitance measurements were used to examine the effects of the sulphonylurea tolbutamide on Ca2+-dependent exocytosis in isolated glucagon-secreting rat pancreatic A-cells. 2. When applied extracellularly, tolbutamide stimulated depolarization-evoked exocytosis 4.2-fold without affecting the whole-cell Ca2+ current. The concentration dependence of the stimulatory action was determined by intracellular application through the recording pipette. Tolbutamide produced a concentration-dependent increase in cell capacitance. Half-maximal stimulation was observed at 33 microM and the maximum stimulation corresponded to a 3.4-fold enhancement of exocytosis. 3. The stimulatory action of tolbutamide was dependent on protein kinase C activity. The action of tolbutamide was mimicked by the general K+ channel blockers TEA (10 mM) and quinine (10 microM). A similar stimulation was elicited by 5-hydroxydecanoate (5-HD; 10 microM), an inhibitor of mitochondrial ATP-sensitive K+ (KATP) channels. 4. Tolbutamide-stimulated, but not TEA-induced, exocytosis was antagonized by the K+ channel openers diazoxide, pinacidil and cromakalim. 5. Dissipating the transgranular K+ gradient with nigericin and valinomycin inhibited tolbutamide- and Ca2+-evoked exocytosis. Furthermore, tolbutamide- and Ca2+-induced exocytosis were abolished by the H+ ionophore FCCP or by arresting the vacuolar (V-type) H+-ATPase with bafilomycin A1 or DCCD. Finally, ammonium chloride stimulated exocytosis to a similar extent to that obtained with tolbutamide. 6. We propose that during granular maturation, a granular V-type H+-ATPase pumps H+ into the secretory granule leading to the generation of a pH gradient across the granular membrane and the development of a positive voltage inside the granules. The pumping of H+ is facilitated by the concomitant exit of K+ through granular K+ channels with pharmacological properties similar to those of mitochondrial KATP channels. Release of granules that have been primed is then facilitated by the addition of K+ channel blockers. The resulting increase in membrane potential promotes exocytosis by unknown mechanisms, possibly involving granular alkalinization.}},
author = {{Hoy, M and Olsen, H L and Bokvist, K and Buschard, K and Barg, Sebastian and Rorsman, Patrik and Gromada, J}},
issn = {{1469-7793}},
language = {{eng}},
number = {{1}},
pages = {{109--120}},
publisher = {{The Physiological Society}},
series = {{Journal of Physiology}},
title = {{Tolbutamide stimulates exocytosis of glucagon by inhibition of a mitochondrial-like ATP-sensitive K+ (KATP) conductance in rat pancreatic A-cells}},
url = {{http://jp.physoc.org/cgi/content/full/527/1/109}},
volume = {{527}},
year = {{2000}},
}