Synthesis of a tritium-labeled indolidan analogue and its use as a radioligand for phosphodiesterase-inhibitor cardiotonic binding sites

Journal Article · Sat Jul 01 04:00:00 EDT 1989 · J. Med. Chem.; (United States)

DOI:https://doi.org/10.1021/jm00127a014· OSTI ID:5604231

Robertson, D W; Krushinski, J H; Utterback, B G; Kauffman, R F

We have radiolabeled a structural analogue of indolidan, a potent phosphodiesterase-inhibitor cardiotonic, to permit biochemical studies regarding the interaction of this class of drugs with their pharmacological receptor. (/sup 3/H)-LY186126 (1,3-dihydro-3,3-dimethyl-1-(/sup 3/H3)methyl-5-(1,4,5,6-tetrahydro-4-me thyl-6- oxo-3-pyridazinyl)-2H-indol-2-one; (/sup 3/H)-3) was selected as a synthetic target because of its potency as a cardiotonic and the ability to readily incorporate three tritia via the indolone N-CH3 substituent. Alkylation of a desmethyl precursor with tritium-labeled iodomethane resulted in (/sup 3/H)-3 with a radiochemical purity of 98% and a specific activity of 79.2 Ci/mmol. This radioligand binds with high affinity to myocardial membrane vesicles. The binding was saturable, and Kd and Bmax values of 4.1 nM and 383 fmol/mg protein were obtained. A series of indolidan congeners displaced (/sup 3/H)-3 bound to myocardial vesicles, and Ki values for inhibition of binding were highly correlated with canine inotropic ED50 values, suggesting the specific binding of (/sup 3/H)-3 to cardiac vesicles is pharmacologically relevant.

• Research Organization: Lilly Corporate Center, Indianapolis, IN (USA)
• OSTI ID: 5604231
• Journal Information: J. Med. Chem.; (United States), Journal Name: J. Med. Chem.; (United States) Vol. 32:7; ISSN JMCMA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
AROMATICS
AZAARENES
AZINES
AZOLES
BIOCHEMICAL REACTION KINETICS
BODY
CARDIOVASCULAR SYSTEM
CELL CONSTITUENTS
CELL MEMBRANES
CHEMICAL PREPARATION
DOGS
ENZYME INHIBITORS
ENZYMES
ESTERASES
HEART
HETEROCYCLIC COMPOUNDS
HYDROLASES
INDOLES
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
LIGANDS
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
MUSCLES
MYOCARDIUM
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PHOSPHODIESTERASES
PROTEINS
PYRIDAZINES
PYRROLES
REACTION KINETICS
RECEPTORS
SPECTROPHOTOMETRY
SYNTHESIS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES