Is the glucose-induced phosphate flush in pancreatic islets attributable to gating of volume-sensitive anion channels?
D-glucose and other nutrient insulin secretagogues have long been known to induce a transient increase in inorganic phosphate release from pancreatic islets, a phenomenon currently referred to as a "phosphate flush". The objective of this study was to explore the possible participation of volume-sensitive anion channels in such a process. Rat pancreatic islets were preincubated for 60 min in the presence of [32P]orthophosphate and then perifused for 90 min to measure 32P fractional outflow rate and insulin secretion. From minutes 46 to 70 inclusive either the concentration of D-glucose was increased from 1.1 to 8.3 mmol L-1 or the extracellular osmolarity was decreased by reducing the NaCl concentration by 50 mmol L-1. The increase in D-glucose concentration induced a typical phosphate flush and biphasic stimulation of insulin release. Extracellular hypoosmolarity caused a monophasic increase in both effluent radioactivity and insulin output. The inhibitor of volume-sensitive anion channels 5-nitro-2-(3-phenylpropylamino)benzoate (0.1 mmol L-1) inhibited both stimulation of insulin release and phosphate flush induced by either the increase in D-glucose concentration or extracellular hypoosmolarity. It is proposed that gating of volume-sensitive anion channels accounts for the occurrence of the phosphate flush and subsequent stimulation of insulin secretion in response to either an increase in D-glucose concentration or a decrease in extracellular osmolarity.
Louchami
Karim
K
Laboratory of Experimental Hormonology, Brussels Free University, 808 Route de Lennik, Brussels, 1070, Belgium.
Zhang
Ying
Y
Beauwens
Renaud
R
Malaisse
Willy J
WJ
Sener
Abdullah
A
D000818:Animals; D005260:Female; D005947:Glucose / Q000378:metabolism*; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D015640:Ion Channel Gating / Q000502:physiology*; D007473:Ion Channels / Q000378:metabolism*; D007515:Islets of Langerhans / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D051381:Rats
D007328:Insulin; D007473:Ion Channels; D010710:Phosphates; D010761:Phosphorus Radioisotopes; D005947:Glucose
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