The influence of diuretic agents on the insulin stimulated glucose metabolism of rat adipose tissue in vitro and in vivo

Abstract

Comparative experiments were carried outin vitro on cell suspensions and cell-free enzyme extracts of epididymal fat tissue andin vivo to find out whether furosemide, acetazolamide and ethacrynic acid have an effect on the insulin-stimulated metabolism of glucose in rat adipose tissue. Typical inhibition curves were used to demonstrate the influence of the concentration of the diuretic agents in a protein-free medium on the oxidation of glucose-1-14C and14CO2-fixation in cell suspensions. Irrespective of the addition of insulin, the inhibition constants for glucose oxidation and CO2-fixation were found to be 2 ⋅ 10−4M for acetazolamide and 5 ⋅ 10−5M for ethacrynic acid. Using furosemide, the maximal inhibition obtained was 30 % at a concentration of 6 ⋅ 10−4M. In each case the addition of albumin to the medium prevented the inhibition completely, presumably due to protein-binding. During incubation with cell-free enzyme extracts none of the diuretic agents affected glucose oxidation or CO2-fixation. In the intact animal the three diuretic agents, administered in doses of 1 ⋅ 100 mg/kg and 8 ⋅ 100 mg/kg, had no effect on the incorporation of14C-glucose into the lipids of fat tissue. After intraperitoneal injection of insulin the incorporation of14C into lipids was increased. The simultaneous administration of 1 ⋅ 100 mg/kg of acetazolamide or ethacrynic acid caused a slight reduction in the incorporation to 80 and 70 % respectively. No such effect was observed with furosemide. The results show that the reduced glucose utilization determined in isolated fat cells is probably of no importancein vivo.