Solubilized musarinic recognition sites from rat brain and heart: evidence in favor of a homogeneous population of sites

Conference · Sat Mar 01 04:00:00 EST 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:5385961

Wang, J; Roeske, W R; Yamamura, H I

The binding characteristics of muscarinic receptors (MAChR) from rat brain and heart (membrane (m-) and 0.5% digitonin solubilized (s-)) were studied at 4/sup 0/C. (/sup 3/H)(-)QNB possessed the same affinity to both m- and s-MAChR (Kd = 20 pM). Pirenzepine (PZ) discriminated two affinities for brain m-MAChR and revealed a single low affinity in heart m-MAChR. S-MAChR from brain and heart displayed similar affinities for PZ ( Ki = 10 and 15 nM). High affinity (/sup 3/H)PZ binding was also found for s-MAChR from both tissues. The receptor affinity for carbachol (CARB) was decreased after solubilization. There was a decrease in the proportion of high affinity state (from 40% to 20% in the brain and from 60% to 15% in the heart) with a 4-fold decrease in the high affinity Ki for CARB. Gpp(NH)p no longer had an effect on the CARB/(/sup 3/H)(-)QNB competition in s-MAChR. Increasing the temperature to 37/sup 0/C caused a 3-6 fold decrease in PZ's affinity to both m- and s-MAChR without altering the ratio of high/low affinity sites. The reduction of PZ's affinity was completely reversible with temperature in m-MAChR and partially reversible in s-MAChR. The authors results suggests that a homogeneous muscarinic recognition site has been solubilized. Solubilization with digitonin results in a separation of the binding site from effector systems and membrane constituents responsible for the tissue specific receptor heterogeneity.

• Research Organization: Univ. of Arizona School of Medicine, Tucson
• OSTI ID: 5385961
• Report Number(s): CONF-8604222-
• Conference Information: Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Journal Volume: 45:3
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ACETYLCHOLINE
AFFINITY
AMINES
AMMONIUM COMPOUNDS
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
BIOCHEMICAL REACTION KINETICS
BODY
BRAIN
CARDIOVASCULAR SYSTEM
CELL CONSTITUENTS
CELL MEMBRANES
CENTRAL NERVOUS SYSTEM
DRUGS
ESTERS
HEART
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
NERVOUS SYSTEM
NEUROREGULATORS
ORGANIC COMPOUNDS
ORGANS
PARASYMPATHOMIMETICS
PROTEINS
QUATERNARY COMPOUNDS
RATS
REACTION KINETICS
RECEPTORS
RODENTS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES