Tolbutamide is a potent inhibitor of cAMP with an IC50 value of 4mM [1].
Tolbutamide has been reported to inhibit both the basal and the cyclic AMP-stimulated protein kinase activites with an IC50 value of 4mM for cyclic AMP-dependent kinase activity. In addition, Tolbutamide has been revealed to inhibit both soluble and membrane-bound protein kinase from canine heart. Moreover, the Tolbutamide inhibition of adipose tissue cyclic AMP- dependent protein kinase is explanation for antilipolytic effects [1]. Besides, Tolbutamide and dbcAMP has been exhibited to increase about four-fold levels of Cx43 mRNA and decrease about 80% the expression of Ki-67 [2].
References:
[1] Wray HL, Harris AW. Adenosine 3', 5'-monophosphate-dependent protein kinase in adipose tissue: inhibition by tolbutamide. Biochem Biophys Res Commun. 1973 Jul 2;53(1):291-4.
[2] Sánchez-Alvarez R1, Paíno T, Herrero-González S, Medina JM, Tabernero A. Tolbutamide reduces glioma cell proliferation by increasing connexin43, which promotes the up-regulation of p21 and p27 and subsequent changes in retinoblastoma phosphorylation. Glia. 2006 Aug 1;54(2):125-34.