[CAS NO. 64-77-7]  Tolbutamide (HLS 831)

Tolbutamide belongs to a class of medications called sulfonylureas. Tolbutamide lowers blood sugar by causing the pancreas to produce insulin (a natural substance that is needed to break down sugar in the body) and helping the body use insulin efficiently. This medication will only help lower blood sugar in people whose bodies produce insulin naturally. Tolbutamide is not used to treat type 1 diabetes (condition in which the body does not produce insulin and, therefore, cannot control the amount of sugar in the blood) or diabetic ketoacidosis (a serious condition that may occur if high blood sugar is not treated). Tolbutamide inhibits both the basal and the cyclic AMP-stimulated protein kinase activities and the IC50 of Tolbutamide is 4 mM. Similar Tolbutamide concentrations are required for half maximal inhibition of in vitro lipolysis induced by hormones (norepinephrine and ACTH) or by dibutyryl cyclic AMP plus theophylline. Tolbutamide also inhibits both soluble and membrane-bound protein kinase from canine heart. The Tolbutamide inhibition of adipose tissue cyclic AMP-dependent protein kinase is one possible explanation for the antilipolytic effects of this drug. Tolbutamide inhibits C6-glioma cell proliferation by increasing Cx43, which correlates with a reduction in pRb phosphorylation due to the up-regulation of the Cdk inhibitors p21 and p27. Cytosolic nucelotides enhance the Tolbutamide sensitivity of the ATP-dependent K+ channel in mouse pancreatic B cells by their combined actions at inhibitory and stimulatory receptors. Tolbutamide inhibits glucagon-induced phosphorylation of the bifunctional enzyme protein in a dose-dependent manner. By adding 2 mM Tolbutamide, reduces activity of 6PF-2-K and increased activity of Fru-2,6-P2ase in the presence of 10(-9) M glucagon are partially restored. The present results suggest the possibility that Tolbutamide modulates the activity of hepatic 6PF-2-K/Fru-2,6-P2ase through inhibiting a phosphorylation of the enzyme protein.