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- Berts, Alf, et al.
(författare)
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Oscillatory Ca2+ signaling in somatostatin-producing cells from the human pancreas
- 1997
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Ingår i: Metabolism. - 0026-0495 .- 1532-8600. ; 46:4, s. 366-369
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Tidskriftsartikel (refereegranskat)abstract
- Oscillatory Ca2+ signaling was studied in human somatostatin-releasing pancreatic δ cells identified by immunostaining. A ratiometric fura-2 technique was used for measuring cytoplasmic concentrations of Ca2+ and Sr2+ in δ cells exposed to the respective cation. Rhythmic activity in terms of slow (frequency, 0.1 to 0.4 per minute) oscillations from close to the basal level was seen in the presence of 3 to 20 mmol/L glucose during superfusion with medium containing 2.6 to 5 mmol/L Ca2+ or 5 mmol/L Sr2. These oscillations could be transformed into a sustained increase by decreasing extracellular Ca2+ or adding 1 mmol/L tolbutamide or 20 nmol/L glucagon. Addition of glucagon to a medium containing 20 mmol/L glucose resulted in the generation of short (< 30 seconds) transients, which disappeared upon exposure to 100 nmol/L of the intracellular Ca2+-adenosine triphosphatase (ATPase) inhibitor thapsigargin. When analyzing small aggregates of islet cells, it became evident that oscillatory activity in δ cells can be synchronous with that in adjacent non—δ cells. It is concluded that secretion of pancreatic somatostatin in man involves Ca2+ signaling similar to that regulating the pulsatile release of insulin.
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| 2. |
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| 3. |
- Berts, Alf, et al.
(författare)
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Suppression of Ca2+ oscillations in glucagon-producing alfa2-cells by insulin/glucose and amino acids
- 1996
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Ingår i: Biochimica et Biophysica Acta. - 0006-3002 .- 1878-2434. ; 1310:2, s. 212-216
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Tidskriftsartikel (refereegranskat)abstract
- The cytoplasmic Ca2+ concentration ([Ca2+]i) was continuously monitored in single glucagon-producing α2-cells isolated from the mouse pancreas and later identified by immunostaining. Up to 60% of the α2-cells exhibited spontaneous [Ca2+]i oscillations (frequency 0.1–0.3/min) in a medium containing 3 mM glucose. In originating from a basal level of 60–100 nM, reaching peak values of 300–400 nM and promptly disappearing after blocking voltage-dependent Ca2+ channels with methoxyverapamil, the oscillations resembled those in insulin-releasing β-cells stimulated by glucose. The oscillatory activity was suppressed when combining elevation of glucose to 20 mM with the addition of 2–2000 ng/ml insulin. Whereas 10 mM of l-arginine or l-glycine transformed the oscillations into sustained elevation of [Ca2+];, there was no response to 1 mM tolbutamide or 0.1–1 mM γ-aminobutyric acid. The observations that α2-cells differ from islet cells secreting insulin and somatostatin in responding to adrenaline with mobilisation of intracellular calcium can be used for their rapid identification. It is suggested that the oscillations reflect periodic entry of Ca2+ due to variations of the membrane potential.
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