Influence of inorganic phosphate on glucose-induced insulin release in vitro

The effect of various extracellular phosphate concentrations on glucose induced insulin secretion has been investigated in two experimental systems the isolated perfused rat pancreas and the isolated rat pancreatic islets incubated in vitro. In both systems, total insulin secretion in response to 16.7 mmol/l glucose increased as extracellular phosphate concentration increased from 0 to 3.6 mmol/l. In perfusion experiments insulin secretion was significantly reduced at 4.8 mmol/l phosphate. In incubation experiments insulin secretion was inhibited only at 9.6 mmol/l phosphate concentration. When IBMX 1 mmol/l was used in incubation experiments glucose induced insulin secretion increased as extracellular phosphate increased from 0 to 3.6 mmol/l, but was also inhibited at 4.8 mmol/l.