Affiliation: | * Department of Biochemistry, University of Ottawa, Ottawa, Ontario, Canada, K1H 8M5 ‡ The Institute for Biological Sciences, National Research Council, Ottawa, Ontario, Canada K1A 0R6 § Biotechnology Research Institute, National Research Council, Monreal, Quebec, Canada |
Abstract: | Glucose-induced insuline release, glucose-induced rises in intracellular free Ca2+ concentration ([Ca2+]i), and voltage-dependent Ca2+ channel activity were assessed in monolayer cultures of β-vells 3–5 day-old rats. The glucose-stimulated insulin secretory responses and [Ca2+]i rises were like those in adult rat β-cells rather than fetal rat β-cells. Voltage-dependent Ca2+ channel antagonists decreased glucose-induced insulin secretion, aborted the [Ca2+]2 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+]1 after membrane depolarization by 45 mMm K+ or 200 μM tolbutamide. Thus, in cultured β-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. |