Insulin secretion and intracellular Ca2+ rises in monolayer cultures of neonatal rat beta-cells.
Glucose-induced insulin release, glucose-induced rises in intracellular free Ca2+ concentration ([Ca2+]i), and voltage-dependent Ca2+ channel activity were assessed in monolayer cultures of beta-cells from 3-5-day-old rats. The glucose-stimulated insulin secretory responses and [Ca2+]i rises were like those in adult rat beta-cells rather than fetal rat beta-cells. Voltage-dependent Ca2+ channel antagonists decreased glucose-induced insulin secretion, aborted the [Ca2+]i rise and, like deprivation of extracellular Ca2+, prevented the glucose-induced rise in [Ca2+]i when added before the glucose challenge. The presence of nifedipine-sensitive, voltage-dependent Ca2+ channels was demonstrated directly by measuring Ca2+ currents using the whole-cell configuration of the patch-clamp technique and indirectly by measuring [Ca2+]i after membrane depolarization by 45 mM K+ or 200 microM tolbutamide. Thus, in cultured beta-cells of 3-5-day-old rats the coupling of glucose stimulation to Ca2+ influx is essentially mature, in contrast to what has been reported for fetal or very early neonatal cells.
Black
M A
MA
Department of Biochemistry, University of Ottawa, Ontario, Canada.
Mealing
G A
GA
Whitfield
J F
JF
Schwartz
J L
JL
Bégin-Heick
N
N
D000367:Age Factors; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D002478:Cells, Cultured; D005260:Female; D005947:Glucose / Q000502:physiology; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D008297:Male; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014044:Tolbutamide / Q000494:pharmacology
D015220:Calcium Channels; D007328:Insulin; D014044:Tolbutamide; D009543:Nifedipine; D005947:Glucose; D011188:Potassium; D002118:Calcium