ATP-INDUCED INTRACELLULAR CA2-SECRETING CELLS( SIGNALS IN ISOLATED HUMAN INSULIN)

Using isolated beta-cells from human islets of Langerhans we have demo nstrated that purinergic receptor agonists are functionally coupled to rises in the intracellular calcium ion concentration ([Ca2+](i)). The effects of ATP, ADP and AMP have been examined over a range of concen trations, 0.5 to 500 mu M. The actions of ATP were more potent than th ose of either ADP or AMP suggesting that a P-2-type of purinergic rece ptor operates in these cells. Responses to ATP were concentration-rela ted, but exhibited marked desensitisation at high concentrations (>100 mu M). Purinergic receptor agonists elevate [Ca2+](i) by mechanisms t hat involve both Ca2+ influx and Ca2+ mobilisation from intracellular stores. The physiological significance of our data has been discussed, and related to previous studies carried out upon rodent and clonal in sulin-secreting cells.