Contribution of the endoplasmic reticulum to the glucose-induced [Ca(2+)](c) response in mouse pancreatic islets.

Content Provider	Semantic Scholar
Author	Arredouani, Abdelilah Henquin, J. -C. Gilon, Patrick
Copyright Year	2002
Abstract	Thapsigargin (TG), a blocker of Ca(2+) uptake by the endoplasmic reticulum (ER), was used to evaluate the contribution of the organelle to the oscillations of cytosolic Ca(2+) concentration ([Ca(2+)](c)) induced by repetitive Ca(2+) influx in mouse pancreatic beta-cells. Because TG depolarized the plasma membrane in the presence of glucose alone, extracellular K(+) was alternated between 10 and 30 mM in the presence of diazoxide to impose membrane potential (MP) oscillations. In control islets, pulses of K(+), mimicking regular MP oscillations elicited by 10 mM glucose, induced [Ca(2+)](c) oscillations whose nadir remained higher than basal [Ca(2+)](c). Increasing the depolarization phase of the pulses while keeping their frequency constant (to mimic the effects of a further rise of the glucose concentration on MP) caused an upward shift of the nadir of [Ca(2+)](c) oscillations that was reproduced by raising extracellular Ca(2+) (to increase Ca(2+) influx) without changing the pulse protocol. In TG-pretreated islets, the imposed [Ca(2+)](c) oscillations were of much larger amplitude than in control islets and occurred on basal levels. During intermittent trains of depolarizations, control islets displayed mixed [Ca(2+)](c) oscillations characterized by a summation of fast oscillations on top of slow ones, whereas no progressive summation of the fast oscillations was observed in TG-pretreated islets. In conclusion, the buffering capacity of the ER in pancreatic beta-cells limits the amplitude of [Ca(2+)](c) oscillations and may explain how the nadir between oscillations remains above baseline during regular oscillations or gradually increases during mixed [Ca(2+)](c) oscillations, two types of response observed during glucose stimulation.
Starting Page	5
Ending Page	9
Page Count	5
File Format	PDF HTM / HTML
Alternate Webpage(s)	http://ajpendo.physiology.org/content/ajpendo/282/5/E982.full.pdf
PubMed reference number	11934662v1
Volume Number	282
Issue Number	5
Journal	American journal of physiology. Endocrinology and metabolism
Language	English
Access Restriction	Open
Subject Keyword	Calcium Diazoxide Endoplasmic Reticulum Glucose Islets of Langerhans Large Membrane Potentials Plasma membrane Potassium Thapsigargin
Content Type	Text
Resource Type	Article