Vanadate Has no Effect on Insulin-Extraction by the Rat Liver

Abstract

The mechanism(s) responsible for the insulin-like effects of vanadate are still unclear, although several possible explanations have been raised. However, the possibility that vanadate induces inhibition of insulin degradation in the liver was not examined yet. Therefore, in the present study we examined the effect of vanadate on the extraction of insulin by the perfused rat liver using an open, non-recycling system. Baseline insulin extraction (44 +/- 2% and 37 +/- 3%) was not affected by the administration of 1 and 5 microM vanadate (decreased to 42 +/- 2% and 36 +/- 1, respectively, p = NS). Vanadate had no adverse effects on liver viability, and the bile flow remained stable during and after vanadate administration (0.87 +/- 0.08 microliter/min/g liver prior to Vs. 0.084 +/- 0.11 microliter/min/g liver following vanadate administration). This study shows that vanadate does not inhibit insulin extraction by the perfused liver, and that does of vanadate that effectively inhibit hepatic glucose production possess no adverse effects on liver viability.