title: Differential identification and localization of adenylyl cyclase and glucose transporter in brain using iodinated derivatives of forskolin.
abstract: Two radioiodinated derivatives of forskolin, [125I]6-IHPP-Fsk and [125I]7-IHPP-Fsk, were synthesized as specific ligands for adenylyl cyclase and glucose transporter, respectively. [125I]6-IHPP-Fsk bound to bovine brain homogenates with a Kd of 9 nM and binding was inhibited by forskolin but not 1,9-dideoxyforskolin, cytochalasin B, or D-glucose. [125I]7-IHPP-Fsk bound to bovine brain homogenates at two classes of binding sites with Kd's of 56 nM and 4.7 microM; cytochalasin B and D-glucose inhibited 75% of the high affinity binding while having no effect on the low affinity binding. [125I]6-IHPP-Fsk and [125I]7-IHPP-Fsk were used to localize adenylyl cyclase and glucose transporter in rat brain by receptor autoradiography. The pattern of binding obtained with [125I]6-IHPP-Fsk was similar to that observed using [3H]forskolin to detect adenylyl cyclase. In contrast, the pattern of binding obtained with [125I]7-IHPP-Fsk was similar to that observed by others using [3H]cytochalasin B to detect glucose transporter. These iodinated ligands are selective for adenylyl cyclase and glucose transporter and require significantly shorter exposure times to yield autoradiographs than tritiated ligands.
authors.affiliation: Molecular Pharmacology Laboratory, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892.
authors.forename: J D
authors.initials: JD
authors.lastname: Robbins
authors.forename: N M
authors.initials: NM
authors.lastname: Appel
authors.forename: A
authors.initials: A
authors.lastname: Laurenza
authors.forename: I A
authors.initials: IA
authors.lastname: Simpson
authors.forename: E B
authors.initials: EB
authors.lastname: De Souza
authors.forename: K B
authors.initials: KB
authors.lastname: Seamon
mesh_terms: D000262:Adenylyl Cyclases / Q000032:analysis*; D000818:Animals; D001921:Brain / Q000201:enzymology; D001923:Brain Chemistry / Q000502:physiology*; D002417:Cattle; D005576:Colforsin / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D003571:Cytochalasin B / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D007457:Iodine Radioisotopes; D015394:Molecular Structure; D009004:Monosaccharide Transport Proteins / Q000032:analysis*; D011869:Radioligand Assay
chemical_list: D007457:Iodine Radioisotopes; D009004:Monosaccharide Transport Proteins; D005576:Colforsin; D003571:Cytochalasin B; D000262:Adenylyl Cyclases; D005947:Glucose; C047983:1,9-dideoxyforskolin