[The effects and mechanism of islet amyloid polypeptide on insulin secretion in INS-1 cells stimulated by glibenclamide].
OBJECTIVE
To observe the effects, and study the mechanism of islet amyloid polypeptide (IAPP) on insulin secretion in INS-1 cells stimulated by glibenclamide.


METHODS
Whole cell patch clamp technique was employed to study the influences of short exposure to IAPP on electrophysiological characteristics of ATP-sensitive K+ channel (K(ATP) channel) upon sulfonylurea stimulation. Intracellular free calcium changes in this process was observed by laser scanning confocal microscope. Insulin was measured by enzyme-linked immunoassay.


RESULTS
(1) Insulin secretion stimulated by 1 micomol/L glibenclamide was significantly decreased from (11.43 +/- 1.22) microg/L to (9.40 +/- 0.87) microg/L and to (7.11 +/- 1.85) microg/L after 1 micromol/L and 10 micromol/L IAPP incubation, respectively. (2) Glibenclamide-stimulated calcium influx was dose dependently inhibited by IAPP from 1 micromol/L to 10 micromol/L, with the AUC of fluorescence intensity-time reduced from 427.78 +/- 2.32 to 380.59 +/- 1.49, and to 246.53 +/- 8.41, respectively. (3) Compared with that in control cells (14.59 +/- 0.69) mV, the half activation voltage of KA, channel in response to glibenclamide was significantly increased to (28.75 +/- 0.77) mV and to (46.95 +/- 1.81) mV in cells pretreated with 1 micromol/L and 10 micromol/L IAPP, implicating an inhibitory effect of IAPP on activation of K(ATP) channel.


CONCLUSIONS
Short-term exposure to high concentration of IAPP inhibited glibenclamide-induced closure of K(ATP) channels and decreased calcium influx, which may ultimately lead to the reduction of insulin secretion in INS-1 cells
Jinfeng
J
Xiao
Xiaotong
X
Li
Xin
X
Zhao
Bingjun
B
He
Xueliang
X
Shang
Lixin
L
Han
Guangyan
G
Wu
Xuemei
X
Ding
Tiehong
T
Zhu
D002118:Calcium; D005947:Glucose; D005905:Glyburide; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D058228:Islet Amyloid Polypeptide / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D013453:Sulfonylurea Compounds
D007328:Insulin; D058228:Islet Amyloid Polypeptide; D013453:Sulfonylurea Compounds; D005947:Glucose; D005905:Glyburide; D002118:Calcium