ISSN:
1432-1424
Keywords:
patch clamp
;
[Ca2+] i
;
Na+ dependency
;
RINm5F cell
;
fura-2
;
whole cell
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary The patch-clamp technique and measurements of single cell [Ca2+] i have been used to investigate the importance of extracellular Na+ for carbohydrate-induced stimulation of RINm5F insulin-secreting cells. Using patch-clamp whole-cell (current-clamp) recordings the average cellular transmembrane potential was estimated to be −60±1 mV (n=83) and the average basal [Ca2+] i 102±6nm (n=37). When challenged with either glucose (2.5–10mm) ord-glyceraldehyde (10mm) the cells depolarized, which led to the initiation of Ca2+ spike potentials and a sharp rise in [Ca2+] i . Similar effects were also observed with the sulphonylurea compound tolbutamide (0.01–0.1mm). Both the generation of the spike potentials and the increase in [Ca2+] i were abolished when Ca2+ was removed from the bathing media. When all external Na+ was replaced with N-methyl-d-glucamine, in the continued presence of either glucose,d-glyceraldehyde or tolbutamide, a membrane repolarization resulted, which terminated Ca2+ spike potentials and attenuated the rise in [Ca2+] i . Tetrodotoxin (TTX) (1–2 μm) was also found to both repolarize the membrane and abolish secretagogue-induced rises in [Ca2+] i .
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01872887
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