New evidence on hypoglycemic effect of quinolinic acid in diabetic rats

In the present study, the effects of administrating 4 mM and 300 mg kg(-1) b.wt. of quinolinic acid were studied, in vitro and in vivo, respectively, to evaluate its inhibitory activity on phosphoenolpyruvate carboxykinase in diabetic rats. The results of in vitro studies have clearly indicated the inhibitory effect of quinolinic acid on enzyme activity. The hill plot showed the binding stoichiometry of quinolinic acid per enzyme to be 4:1. The in vivo studies showed that intra peritoneal injection of 300 mg kg(-1) b.wt. initiates reduction of blood glucose level in 1 h after injection, restoring the blood glucose to its normal level at 2 h post injection and keeping it constant for at least further 4 h. Based on present results we concluded that quinolinic acid and hence its precursor tryptophan having induced obvious hypoglycemic effects in normal and diabetic rats at high enough concentrations, they are worthy of further study and research for their hyperglycemic effect in other diabetic animal models.