DIFFERENT EFFECTS OF GLUCOSE AND GLYBURIDE ON INSULIN-SECRETION IN RAT PANCREATIC-ISLETS PREEXPOSED TO INTERLEUKIN-1-BETA - POSSIBLE INVOLVEMENT OF K+ AND CA2+ CHANNELS
M. Buscema et al., DIFFERENT EFFECTS OF GLUCOSE AND GLYBURIDE ON INSULIN-SECRETION IN RAT PANCREATIC-ISLETS PREEXPOSED TO INTERLEUKIN-1-BETA - POSSIBLE INVOLVEMENT OF K+ AND CA2+ CHANNELS, Diabetologia, 36(9), 1993, pp. 791-796
Citations number
32
Categorie Soggetti
Endocrynology & Metabolism","Medicine, General & Internal
In vitro islet exposure to interleukin 1beta inhibits the beta-cell re
sponse to glucose. We have studied whether a similar inhibition also o
ccurs in response to the sulphonylurea glyburide. Rat pancreatic islet
s were cultured for 24 h in the presence or absence of 50 U/ml interle
ukin 1beta and then stimulated with either glucose or glyburide for 1
h at 37-degrees-C. In control islets basal insulin secretion was 117 /- 32 pg . islet-1 h-1 (mean +/- SEM, n = 7) and greatly increased in
response to 16.7 mmol/l glucose (2140 +/- 293) or 10 mumol/l glyburide
(1464 +/- 234). When islets were pre-exposed to interleukin 1beta, in
sulin release was significantly reduced in response to glucose (323 +/
- 80, p < 0.001) but not in response to glyburide (1316 +/- 185). Sinc
e both glucose and glyburide influence beta-cell K+ and Ca2+ efflux, t
o further investigate this different response in islets exposed to int
erleukin 1beta we measured both Rb- efflux (as index of the ATP-sensit
ive K+ channel activity) and Ca2+ uptake. In control islets, the incre
ased insulin secretion in response to 16.7 mmol/l glucose or 10 mumol/
l glyburide was associated with a reduction of Rb-86 efflux (decrement
of -50 +/- 1.2 % and -49 +/- 2.3 %, respectively, mean +/- SEM, n = 5
). In contrast, in interleukin 1beta pre-exposed islets both glucose a
nd glyburide stimulation only slightly modified Rb-86 efflux (decremen
t of -19 +/- 1.9 % and -5.3 +/- 3.1 %, respectively, n = 5, p < 0.001
). Ca-45(2+) uptake in control islets was 2.6 +/- 0.4 mumol . islet-1
. 20 min-1 under basal conditions (at 2.8 mmol/l glucose), and increas
ed to 16.8 +/- 3.2 and 10.7 +/- 2.1 pmol . islet-1. 20 min-1 in islets
stimulated with 16.7 mmol/I glucose or 10 mumol/l glyburide, respecti
vely (mean +/- SEM, n = 6). Ca-45(2+) uptake in interleukin 1beta trea
ted is lets was higher than in control islets under basal conditions (
4.6 +/- 0.6 pmol . islet-1. 20 min-1 at 2.8 mmol/l glucose, p < 0.05),
but was significantly reduced in response to glucose 16.7 mmol/l (7.1
+/- 1.1, p < 0.01 with respect to control islets). In contrast to glu
cose, 10 mumol/l glyburide was able to stimulate calcium uptake in int
erleukin 1beta treated islets in a similar way to control islets (12.8
+/- 2.5). The present data demonstrate that rat pancreatic islets tre
ated with interleukin 1beta for 24 h lose their responsivity to glucos
e, but not to glyburide. The difference between the two secretagogues
is associated with the persistent ability of glyburide to influence Ca
2+ uptake even in islets with impaired K+-channel function.