Effect of tolbutamide on lipolytic processes in blood and fat tissue of rats maintained in normothermic and hypothermic conditions

: The effect of tolbutamide administered in vivo or added to the incubation medium on lipolysis in adipose tissue and in blood has been studied in rats. Tissue lipolysis was lowered by 118 to 156% in groups of rats receiving tolbutamide in vivo. The addition of tolbutamide directly to the incubation medium caused an increase in the lipid mobilizing activity, while the addition of insulin inhibited lipolysis in each case. The effect of tolbutamide administered in vivo may be indirect through an increase in insulin binding and/or the drug may influence directly the permeability of cell membrane for ions and glucose. An increase in the lipid mobilizing activity observed in experiments consisting in the addition of tolbutamide to the incubation medium may be linked to the low glucose level and greater demand for free fatty acids or to the low level of insulin in the incubation medium.