ISSN:
1432-1424
Keywords:
patch-clamp
;
fura-2
;
KATP channels
;
[Ca2+] i
;
insulin-secreting cell
;
RINm5F cell
;
diazoxide
;
cromakalim (BRL 34915)
;
tolbutamide
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary Patch-clamp and single cell [Ca2+] i measurements have been used to investigate the effects of the potassium channel modulators cromakalim, diazoxide and tolbutamide on the insulin-secreting cell line RINm5F. In intact cells, with an average cellular transmembrane potential of −62±2 mV (n=42) and an average basal [Ca2+] i of 102±6nm (n=37), glucose (2.5–10mm): (i) depolarized the membrane, through a decrease in the outward KATP current, (ii) evoked Ca2+ spike potentials, and (iii) caused a sharp rise in [Ca2+] i . In the continued presence of glucose both cromakalim (100–200 μm) and diazoxide (100 μm) repolarized the membrane, terminated Ca2+ spike potentials and attenuated the secretagogue-induced rise in [Ca2+] i . In whole cells (voltage-clamp records) and excised outside-out membrane patches, both cromakalim and diazoxide enhanced the current by opening ATP-sensitive K+ channels. Diazoxide was consistently found to be more potent than cromakalim. Tolbutamide, a specific inhibitor of ATP-sensitive K+ channels, reversed the effects of cromakalim on membrane potential and KATP currents.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01869384
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