Dual effect of ATP on glucose-induced insulin secretion in HIT-T15 cells

OBJECTIVES:: The study investigated the dual effect of purinergic nucleotides on the secretion of insulin from pancreatic β cells. METHODS:: The level of insulin secretion in HIT-T15 cells of static incubation was measured using a radioimmunoassay. RESULTS:: The adenine nucleotides reduced the level of glucose-induced insulin secretion in a concentration-dependent manner, and the relative potency order (IC50; μM) was BzATP (6.9) > ATP (20.4) ≥ α, β-methylene ATP (23.3) ≥ 2-methylthio-ATP (24.9). Suramin and PPADS (200 μM), which are blockers of the purinergic receptors, had a little influence on the activity of ATP. However, the inhibitory effect of ATP was reversed by preincubation with oxidized ATP (200 μM), which is a P2X7 antagonist. The level of insulin secretion in these preincubated cells exposed to the purinergic nucleotides increased in the following order: ATP > α, β-methylene ATP ≥ 2-methylthio-ATP. A pretreatment with foskolin and PDBu (100 nM) potentiated the increasing effect of ATP on insulin secretion. The Western blotting showed the expression of P2X7 and P2Y11 receptors. CONCLUSIONS:: Purinergic stimulation has inhibitory activity on glucose-dependent insulin secretion through the activation of the P2X7 receptor, whereas it has enhancing effect through the activation of the P2Y11 receptor in HIT-T15 cells.