Glucose stimulation of somatostatin-producing islet cells involves oscillatory Ca2+ signaling.
The cytoplasmic Ca2+ concentration ([Ca2+]i) was measured with fura-2 in individual mouse pancreatic delta-cells identified by immunostaining for somatostatin. A majority of the delta-cells responded to 3 mM glucose with slow oscillations of [Ca2+]i (frequency, 0.1-0.4/min). In originating from a basal level of 60-100 nM and reaching peak values of 200-500 nM, the oscillations resembled those in insulin-secreting beta-cells stimulated by glucose. The rise in glucose to 20 mM resulted in a minor increase in the oscillatory frequency and sometimes in transformation of the oscillations into sustained elevation of [Ca2+]i. The addition of 3 microM L-epinephrine effectively counteracted the increase in [Ca2+]i in response to glucose. The delta-cells reacted with a sustained elevation of [Ca2+]i after raising extracellular K+ to 30.9 mM or adding 1 microM tolbutamide. Analyses using the patch-clamp technique revealed the presence of K+ channels with properties similar to the ATP-sensitive channels in pancreatic beta-cells. It is concluded that regulation of somatostatin release mimics that of insulin, with glucose induction of [Ca2+]i oscillations.
Berts
A
A
Department of Medical Cell Biology, Uppsala University, Sweden.
Ball
A
A
Dryselius
G
G
Gylfe
E
E
Hellman
B
B
D000818:Animals; D002118:Calcium / Q000502:physiology*; D003593:Cytoplasm / Q000378:metabolism; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D005947:Glucose / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008815:Mice, Inbred Strains; D009991:Oscillometry; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology; D015398:Signal Transduction; D013004:Somatostatin / Q000096:biosynthesis*
D015221:Potassium Channels; D013004:Somatostatin; D005947:Glucose; D002118:Calcium; D004837:Epinephrine