Studies on the N-[(trans-4-isopropylcyclohexyl)-carbonyl]-D-phenylalanin e (A-4166)receptor in HIT T-15 cells. Displacement of [3H]glibenclamide.
A-4166 is a new type of oral hypoglycemic agent that does not contain a sulfonylurea moiety. To clarify the mechanism of insulin secretion by A-4166, a specific receptor for A-4166 was investigated in a hamster pancreatic beta cell line (HIT T-15), using [3H]A-4166 or [3H]glibenclamide as a ligand. The saturation binding of [3H]A-4166 to HIT cell membranes was not observed up to 10 microM. In the displacement study, unlabeled A-4166 inhibited [3H]A-4166 binding to HIT cell membranes, but glibenclamide did not. On the other hand, A-4166 inhibited [3H]glibenclamide binding to the sulfonylurea receptor (Ki = 248 nM). A-4166 inhibited 86Rb efflux from HIT cells (IC50 = 350 nM). The EC50 for insulin secretion by A-4166 was 20 microM in HIT cells when they were incubated for 30 min in Krebs-Ringer bicarbonate buffer containing 16 mM HEPES supplemented with 5 mg/mL BSA in the absence of glucose. These data demonstrate the possibility of the presence of two kinds of binding sites for A-4166: one of them is the sulfonylurea receptor, and the other might be a binding site specific for A-4166.
Fujita
T
T
Pharmaceutical Institute, Keio University School of Medicine, Tokyo, Japan.
Seto
Y
Y
Kondo
N
N
Kato
R
R
D000818:Animals; D001665:Binding Sites; D006224:Cricetinae; D003510:Cyclohexanes / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005905:Glyburide / Q000378:metabolism*; D007004:Hypoglycemic Agents / Q000378:metabolism*; D051379:Mice; D000077715:Nateglinide; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000378:metabolism; D011869:Radioligand Assay
D003510:Cyclohexanes; D007004:Hypoglycemic Agents; D000077715:Nateglinide; D010649:Phenylalanine; D005905:Glyburide