Specific binding of (/sup 3/H)substance P to the rat submaxillary gland. The effects of ions and guanine nucleotides

Journal Article · Thu Aug 01 00:00:00 EDT 1985 · J. Pharmacol. Exp. Ther.; (United States)

OSTI ID:5023885

Bahouth, S W; Musacchio, J M

(/sup 3/H)Substance P ((/sup 3/H)SP), in a high ionic strength incubation medium, binds to a single class of saturable, noninteracting binding sites on rat submaxillary gland membranes with a KD = 2.8 +/- 0.34 nM and maximum binding (Bmax) = 220 +/- 31 fmol/mg of protein. The rank order of potency of various tachykinins, SP fragments and analogs to compete against (/sup 3/H)SP is correlated with their potency to induce salivation. These findings indicate that, under the conditions described, (/sup 3/H)SP binds to a physiologically relevant tachykinin receptor of the SP-P subtype. (/sup 3/H)SP binding increases by 35% in the presence of optimal concentrations of Mn++ and Mg++ whereas guanine nucleotides reduce (/sup 3/H)SP binding. The effect produced by either divalent cations or guanine nucleotides is due to increasing or decreasing the Bmax, respectively, without changing the affinity of (/sup 3/H)SP. Guanine nucleotides reduce the Bmax of (/sup 3/H)SP to the same level in the presence or absence of divalent cations, indicating that divalent cations increase the population of SP receptors that are sensitive to guanine nucleotides. In low ionic strength media, and when the nonspecific binding is defined by 1 microM SP, (/sup 3/H)SP binds to two sites: a high affinity site with a KD of 0.14 nM and a Bmax of 370 fmol/mg of protein and a low affinity high capacity site. When the nonspecific binding is defined by 1 microM physalaemin, the high affinity is the only detectable site. However, in low ionic strength media, physalaemin has about one-fiftieth the potency of SP in competing with (/sup 3/H)SP.

• Research Organization: New York Univ. Medical Center, NY
• OSTI ID: 5023885
• Journal Information: J. Pharmacol. Exp. Ther.; (United States), Journal Name: J. Pharmacol. Exp. Ther.; (United States) Vol. 2; ISSN JPETA
• Country of Publication: United States
• Language: English

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550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AFFINITY
ALKALINE EARTH METAL COMPOUNDS
AMINES
ANIMALS
AROMATICS
AZAARENES
BIOCHEMICAL REACTION KINETICS
CARDIOVASCULAR AGENTS
CATIONS
CELL CONSTITUENTS
CELL MEMBRANES
CHARGED PARTICLES
DRUGS
GUANINE
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
IN VITRO
IONS
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
MAGNESIUM COMPOUNDS
MAMMALS
MANGANESE COMPOUNDS
MEMBRANES
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
PURINES
RATS
REACTION KINETICS
RODENTS
SULFATES
SULFUR COMPOUNDS
TRACER TECHNIQUES
TRANSITION ELEMENT COMPOUNDS
TRITIUM COMPOUNDS
VALENCE
VASODILATORS
VERTEBRATES