Pirenzepine binding to membrane-bound, solubilized and purified muscarinic receptor subtypes

Conference · Thu May 01 00:00:00 EDT 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:5097533

Baumgold, J

Muscarinic receptors were purified to near-homogeneity from bovine cortex, an area rich in the putative M1 subtype, and from bovine pons/medulla, an area rich in the putative M2 subtype. In both cases, the receptors were solubilized in digitonin and purified over an affinity column. Both the cortical and pons/medulla preparations yielded receptor proteins of 70,000 daltons. Pirenzepine binding was deduced from its competition with /sup 3/H-N-methyl scopolamine. The binding of pirenzepine to membrane-bound receptors from cortex was best described by a two site model, with approximately half the sites having a Ki of 6.4 x 10/sup -9/ M and the remaining sites having a Ki of 3.5 x 10/sup -7/ M. Membrane-bound receptors from pons/medulla bound pirenzepine according to a one-site model with a Ki of 1.1 x 10/sup -7/ M. After solubilization the two-site binding of cortical receptors became a one-site binding, Ki = 1.1 x 10/sup -7/M. This value was still five-fold lower than that of soluble receptors from pons/medulla. After purification however the affinity of pirenzepine for the pons/medulla receptor increased so that the two putative subtypes bound pirenzepine with approximately the same affinity. These findings suggest that the different pirenzepine binding characteristics used to define muscarinic receptor subtypes are not inherent in the receptor protein itself but may be due to coupling factors associated with the receptor.

• Research Organization: NIMH, Bethesda, MD
• OSTI ID: 5097533
• Report Number(s): CONF-8606151-
• Journal Information: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Vol. 45:6; ISSN FEPRA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AFFINITY
ALCOHOLS
AMINES
AMMONIUM COMPOUNDS
ANIMALS
BIOCHEMICAL REACTION KINETICS
BODY
BRAIN
CATTLE
CELL CONSTITUENTS
CELL MEMBRANES
CENTRAL NERVOUS SYSTEM
CENTRAL NERVOUS SYSTEM AGENTS
CHOLINE
DOMESTIC ANIMALS
DRUGS
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
LIPOTROPIC FACTORS
MAMMALS
MATHEMATICAL MODELS
MEMBRANE PROTEINS
MEMBRANES
NERVOUS SYSTEM
ORGANIC COMPOUNDS
ORGANS
PROTEINS
PSYCHOTROPIC DRUGS
PURIFICATION
QUATERNARY COMPOUNDS
REACTION KINETICS
RECEPTORS
RUMINANTS
TRACER TECHNIQUES
TRANQUILIZERS
TRITIUM COMPOUNDS
VERTEBRATES