Receptors for substance P on isolated intestinal smooth muscle cells of the guinea pig

Journal Article · Sat Oct 31 23:00:00 EST 1987 · Am. J. Physiol.; (United States)

OSTI ID:5607695

Souquet, J C; Bitar, K N; Grider, J R; Makhlouf, G M

Two radioligands, /sup 125/I-labeled substance P (/sup 125/I-SP) and /sup 125/I-labeled substance K (/sup 125/I-SK), were used to characterize the kinetics and stoichiometry of binding of mammalian tachykinins (substance P (SP), substance K (SK), and neuromedin K (NK)) to smooth muscle cells isolated from the longitudinal muscle layer of guinea pig intestine. Specific binding of /sup 125/I-SP and /sup 125/I-SK was rapid, saturable, reversible, and temperature dependent. Binding attained 63-70% of steady-state binding within 1 min, coincidentally with the time of optimal contraction. The order of potency with which mammalian tachykinins and the SP antagonist, (D-Pro2, D-Trp7,9)SP, inhibited the binding of both radioligands was identical: SP greater than SK greater than NK greater than (D-Pro2, D-Trp7,9)SP, implying preferential interaction with a site that had highest affinity for SP. SK was 2-3 times, NK 3-4 times, and (D-Pro2, D-Trp7,9)SP 7-23 times less potent than SP (IC50 0.36 nM). Except for NK, the order of potency was similar to that for contraction of isolated muscle cells. The existence of binding sites with even higher affinity was suggested by the ability of muscle cells to contract in response to concentrations as low as 10(-13) M. These binding sites were not detectable at the concentration of radioligands used. It was concluded that a SP receptor is the only tachykinin receptor subtype present on intestinal muscle cells of the guinea pig.

• Research Organization: Medical College of Virginia, Richmond
• OSTI ID: 5607695
• Journal Information: Am. J. Physiol.; (United States), Journal Name: Am. J. Physiol.; (United States) Vol. 253; ISSN AJPHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AFFINITY
ANIMALS
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BODY
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
ELECTRON CAPTURE RADIOISOTOPES
GASTROINTESTINAL TRACT
GUINEA PIGS
INTERMEDIATE MASS NUCLEI
INTESTINES
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGANDS
MAMMALS
MEMBRANE PROTEINS
MUSCLES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
PEPTIDES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RECEPTORS
RODENTS
STOICHIOMETRY
TEMPERATURE DEPENDENCE
TRACER TECHNIQUES
VERTEBRATES