An activation of volume-sensitive anion channels (VSAC) may participate in the depolarization of the plasma membrane induced by high concentrations of D-glucose in insulin secretory B-cells of the endocrine pancreas. In the present study, we have used the outflow of tritiated aspartate from prelabeled isolated rat pancreatic islets, in order to assess the activity of these channels. First, we have characterized the net uptake of D-[2,3-³H]-aspartate by islets. This process is found to be time-, concentration- and temperature-dependent, but is independent of glucose concentration. Over 60 min incubation at 37°C, in the presence of 8.3 mM of D-glucose, the net uptake of D-[2,3-³H]-aspartate (1 mM) averaged 5.99 0.28 fmol/islet (n=47). In prelabeled, then perifused islets at a constant D-glucose concentration of 8.3 mM, a 100 mOsmol/l decrease in the perifusion medium induced a dramatic - more than 4 times - increase in D-[2,3-³H]-aspartate fractional outflow rate (FOR). The FOR averaged 5.44 0.15 10^-3/min (n=4) during the basal period and reached a peak value of 23.14 3.37 10^-3/min (n=4) under hypoosmolar condition. Such a result indicates that tritiated aspartate outflow recording is indeed suitable to evaluate the gating of VSAC in islets. In the last set of experiments, we have focused on the effects of increasing concentrations of D-glucose on tritiated aspartate efflux. The prelabeled islets were first perifused in a glucose-free medium, they were then exposed to an increase of D-glucose concentration, either: 2.8, 5.6, 8.3 or 16.7 mM. No significant change was observed for the lowest glucose concentration. On the other hand, for the highest concentrations, the increases integrated over the whole period of stimulation were, respectively: 32.1 4.9 % (n=4), 46.7 8.8 % (n=6) and 51.5 4.6 % (n=6). These last results strongly suggest that a rise in D-glucose concentration induces the opening of volume-sensitive anion channels.