Oscillatory Signaling and Insulin Release in Human Pancreatic -Cells Exposed to Strontium

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Abstract
Oscillatory signaling and insulin release were studied in isolated pancreatic islets and b-cells obtained from human cadaveric organ donors. Taking advantage of Sr21 as an analog for Ca21 ,i t was possible to demonstrate glucose-induced rhythmic activity in indi- vidual b-cells identified by immunostaining. Glucose-induced slow oscillations of Sr21 (frequency, 0.1-1.0/min) were sometimes seen at a sugar concentration as low as 3 mM. Addition of 20 nM glucagon resulted in a broadening of the oscillations or in their transformation into sustained elevation. Moreover, the presence of glucagon resulted in the appearance of short transients of Sr21, which disappeared after exposure to the intracellular Ca21-adenosine triphosphatase inhibi- tor thapsigargin. Digital image analyses indicated that slow oscilla- tions can be synchronized among cells in small aggregates and intact islets. The rhythmic activity in the glucose-stimulated b-cell had its counterpart in pulsatile insulin release when single islets were peri- fused with a Sr21-containing medium. It is concluded that the human b-cell has oscillatory signaling for insulin release similar to that observed in experimental animals. (Endocrinology 138: 3161-3165, 1997)

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