( sup 3 H)idazoxan binding to the ovine myometrium. Binding characteristics and changes due to steroid hormones

Journal Article · Tue May 01 04:00:00 EDT 1990 · Journal of Pharmacology and Experimental Therapeutics; (USA)

OSTI ID:6747079

Vass-Lopez, A; Garcia-Villar, R; Lafontan, M; Toutain, P L ^[1]

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1. Institut National de la Recherche Agronomique, Toulouse (France)

(3H)idazoxan binding to myometrial membranes was investigated in four groups of ewes under different steroid hormone status: control, estradiol-treated and progesterone plus estradiol-treated ovariectomized ewes and pregnant ewes. (3H)idazoxan binding to myometrial membrane fractions was saturable, reversible, specific and of high affinity. The affinity did not vary significantly between the four groups of ewes (2.8 less than KD less than 4.7 nM). Maximal binding capacity varied significantly among groups: binding of (3H)idazoxan was lower in control ovariectomized ewes than in either estradiol or progestagen plus estrogen-treated ewes (maximal binding capacity, 73 +/- 11 fmol/mg of protein vs. 108 +/- 16 and 318 +/- 65, respectively). The highest (3H)idazoxan binding was measured in pregnant ewes (maximal binding capacity, 1302 +/- 256 fmol/mg of protein). Based on the saturation studies with accurate nonspecific binding definition (phentolamine vs. epinephrine), and on the relative order of potency for selected adrenergic drugs, it could be stated that the binding sites labeled by (3H)idazoxan in our study exhibited most of the alpha-2 adrenoceptor properties. Nevertheless, these alpha-2 adrenoceptors obviously differed from the standard alpha-2A-subtype based on Ki values obtained with yohimbine and prazosin in competition studies of (3H)idazoxan binding. The increase in the number of alpha-2 adrenoceptors under progesterone domination, and especially during gestation, supported the hypothesis that this adrenoceptor subtype could play a major role in the control of the motility pattern of the ovine pregnant uterus.

• OSTI ID: 6747079
• Journal Information: Journal of Pharmacology and Experimental Therapeutics; (USA), Journal Name: Journal of Pharmacology and Experimental Therapeutics; (USA) Vol. 253:2; ISSN JPETA; ISSN 0022-3565
• Country of Publication: United States
• Language: English

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550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AFFINITY
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
BIOCHEMICAL REACTION KINETICS
BODY
CELL CONSTITUENTS
CELL MEMBRANES
DOMESTIC ANIMALS
DRUGS
ESTRADIOL
ESTRANES
ESTROGENS
FEMALE GENITALS
GONADS
HORMONES
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
KETONES
KINETICS
MAMMALS
MEMBRANE PROTEINS
MEMBRANES
ORGANIC COMPOUNDS
ORGANS
OVARIES
PARASYMPATHOLYTICS
PARASYMPATHOMIMETICS
PREGNANCY
PREGNANES
PROGESTERONE
PROTEINS
REACTION KINETICS
RECEPTORS
RUMINANTS
SHEEP
STEROID HORMONES
STEROIDS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES