Inhibitory effects of amiloride on alpha adrenoceptors in canine vascular smooth muscle

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

OSTI ID:6727750

Shi, A G; Wang, Z L; Kwan, C Y; Daniel, E E ^[1]

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1. McMaster Univ., Hamilton, Ontario (Canada)

Amiloride inhibits vascular smooth muscle contractions from canine aorta and saphenous vein. The mechanisms were studied using radioligand binding and functional techniques. Amiloride inhibited ({sup 3}H)prazosin and ({sup 3}H)rauwolscine binding to alpha-1 and alpha-2 adrenoceptors in a concentration-dependent manner. Amiloride increased Kd values for ({sup 3}H)rauwolscine without affecting the maximum binding of ({sup 3}H)prazosin. These results suggest that the drug interacts with the alpha-1 adrenoceptor binding sites in a competitive manner and with the alpha-2 adrenoceptor binding sites in a noncompetitive manner. Amiloride reduced maximal contractile responses to agonists selective for both alpha adrenoceptors and to elevated K+, the EC50 values were increased by about 10-fold in the presence of amiloride. In Ca+(+)-free Krebs' solution, contractions induced in saphenous vein after addition of Ca++ in saphenous vein in the presence of adrenoceptor agonists were inhibited by amiloride. Our results suggest that amiloride reduced alpha-1 and alpha-2 adrenoceptor-mediated responses and inhibited Ca++ influx.

• OSTI ID: 6727750
• Journal Information: Journal of Pharmacology and Experimental Therapeutics; (USA), Vol. 253:2; ISSN 0022-3565
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
DIURETICS
BIOCHEMICAL REACTION KINETICS
MUSCLES
VASOCONSTRICTION
PARASYMPATHOMIMETICS
RECEPTORS
CALCIUM COMPOUNDS
CELL CULTURES
DOGS
INHIBITION
MEMBRANE TRANSPORT
MICROSOMES
RADIOASSAY
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
CELL CONSTITUENTS
DRUGS
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
KINETICS
MAMMALS
MEMBRANE PROTEINS
ORGANIC COMPOUNDS
ORGANOIDS
PROTEINS
REACTION KINETICS
RIBOSOMES
VERTEBRATES
550201* - Biochemistry- Tracer Techniques