Heterogeneous changes in [Ca2+]i induced by glucose, tolbutamide and K+ in single rat pancreatic B cells.
The effects of glucose, tolbutamide and K+ on cytosolic free Ca2+ ([Ca2+]i) in single rat pancreatic B cells were examined using Fura-2 and dual wavelength microfluorimetry. At basal glucose concentration (2.8 mM), about half of the cells were found to display spontaneous Ca2+ oscillations. Glucose (greater than or equal to 11.1 mM), tolbutamide (greater than or equal to 50 microM) and K+ (50 mM) induced rises in [Ca2+]i that could be inhibited by the Ca2+ channel blocker D600. The pattern of response and the sensitivity to the secretagogues were characterized by a marked heterogeneity. The majority of the cells responded to glucose and tolbutamide by a progressive increase in [Ca2+]i onto which sinusoidal oscillations were superimposed. The periodicity of these oscillations was about 2.5/min. Occasionally, some cells displayed slow and major waves in Ca2+ levels (about 0.2/min). None of the cells responded to glucose by displaying an initial decrease in [Ca2+]i. Likewise, the sugar failed to decrease [Ca2+]i in the absence of extracellular Ca2+. The present study shows that, despite a large heterogeneity of the response, the majority of the pancreatic B cells respond to different secretagogues by displaying fast [Ca2+]i oscillations that are reminiscent of the bursts of electrical activity recorded in B cells.
Herchuelz
A
A
Laboratory of Pharmacology, Brussels Free University School of Medicine, Belgium.
Pochet
R
R
Pastiels
C
C
Van Praet
A
A
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003592:Cytophotometry; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005455:Fluorescent Antibody Technique; D016257:Fura-2; D005947:Glucose / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D014044:Tolbutamide / Q000494:pharmacology*
D014044:Tolbutamide; D005947:Glucose; D011188:Potassium; D002118:Calcium; D016257:Fura-2