( sup 3 H)QNB binding and contraction of rabbit colonic smooth muscle cells

Journal Article · Sun Nov 01 04:00:00 EST 1987 · American Journal of Physiology; (USA)

OSTI ID:7191809

Ringer, M J; Hyman, P E; Kao, H W; Hsu, C T; Tomomasa, T; Snape, Jr, W J ^[1]

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1. Univ. of California, Los Angeles (USA)

The authors used radioligand binding and studies of cell contraction to characterize muscarinic receptors on dispersed smooth muscle cells from rabbit proximal and distal colon. Cells obtained after serial incubations in collagenase were used to measure binding of tritiated quinuclidinyl benzilate (({sup 3}H)QNB). At 37{degree}C, specific ({sup 3}H)QNB binding was saturable and linearly related to cell number. Nonlinear regression analysis was used to determine the affinity of ({sup 3}H)QNB for its receptor. The IC{sub 50} for the muscarinic agonists bethanechol and oxotremorine were 80 and 0.57 {mu}M, respectively. Hill coefficients were 0.67 for both, suggesting more complex interaction involving receptors of different affinities. In studies of cell contraction, bethanechol stimulated a dose-dependent decrease in cell length with half the maximal contraction occurring at 100 pM. These results suggest that (1) contraction is mediated by binding of bethanechol to M{sub 2}-muscarinic receptors and that (2) there are a large number of spare receptors in colonic smooth muscle.

• OSTI ID: 7191809
• Journal Information: American Journal of Physiology; (USA), Journal Name: American Journal of Physiology; (USA) Vol. 253:5; ISSN 0002-9513; ISSN AJPHA
• Country of Publication: United States
• Language: English

Related Subjects

551001* -- Physiological Systems-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
BENZILIC ACID
BIOCHEMICAL REACTION KINETICS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CROSS-LINKING
DOSE-RESPONSE RELATIONSHIPS
HYDROGEN COMPOUNDS
HYDROXY ACIDS
KINETICS
LIGANDS
MEMBRANE PROTEINS
MOLECULAR BIOLOGY
MUSCLES
ORGANIC ACIDS
ORGANIC COMPOUNDS
PHYSIOLOGY
POLYMERIZATION
PROTEINS
REACTION KINETICS
RECEPTORS
TRITIUM COMPOUNDS