Rapid oscillation of insulin release by the rat pancreatic islets under stringent Ca2+-free conditions.
Oscillation of insulin release by the pancreatic islets was evaluated under stringent Ca(2+)-free conditions for the first time. Isolated single rat islets were exposed to 16.7 mM glucose in the presence of 1.9 mM Ca(2+), or under the stringent Ca(2+)-free conditions (Ca(2+) omission with 1 mM EGTA, 6 microM forskolin and 100 nM phorbol 12-myristate 13-acetate). Fifteen minutes after the initiation of glucose stimulation, effluent was collected at a 6-s interval, insulin was determined in duplicate by a highly sensitive insulin radioimmunoassay, and oscillation and pulsatility of release statistically analyzed. Significant oscillation of insulin release was observed in all islets irrespective of presence and absence of Ca(2+). Significant pulsatility of release was detected in 7 of 11 islets in the presence of Ca(2+) and three of six isl! ets in the absence of Ca(2+). In conclusion, high glucose elicits oscillatory insulin release both in the presence and absence of extracellular Ca(2+).
Aizawa
T
T
Department of Geriatrics, Endocrinology and Metabolism, Shinshu University School of Medicine, Matsumoto, Japan. traizawa@hsp.md.shinshu-u.ac.jp
Kaneko
T
T
Yajima
H
H
Yamada
S
S
Sato
Y
Y
Kanda
Y
Y
Kanda
S
S
Noda
M
M
Kadowaki
T
T
Nagai
M
M
Yamauchi
K
K
Komatsu
M
M
Hashizume
K
K
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D005947:Glucose / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012636:Secretory Rate
D007328:Insulin; D005947:Glucose; D002118:Calcium