Relationship between alpha/sub 1/-adrenergic receptor occupancy and regulation of intracellular Ca/sup + +/ in BC3H-1 muscle cells

Conference · Thu May 01 04:00:00 EDT 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:7108457

Brown, R D; Berger, K D; Button, D; Taylor, P

The relationship between ..cap alpha../sub 1/-adrenergic receptor occupancy by agonists or antagonists and functional response was examined. Receptor occupancy was measured using the antagonist (/sup 3/H)prazosin, and correlated with agonist-elicited unidirectional /sup 45/Ca/sup + +/ efflux. The agonists epinephrine (E), norepinephrine (NE), and phenylephrine (PE) activated /sup 45/Ca/sup + +/ efflux with the order of potency expected for ..cap alpha../sub 1/ receptors (E greater than or equal to NE > PE). A parabolic relationship suggesting the presence of a modest receptor reserve was observed between the number of activatable receptors after equilibration with specified (/sup 3/H)prazosin concentrations and residual /sup 45/Ca/sup + +/ efflux responses elicited by E or NE. A linear relationship was previously observed for PE. Agonist occupancy was independently measured by competition with the initial rate of (/sup 3/H)prazosin association. Both E and NE inhibited (/sup 3/H)prazosin binding over higher concentration ranges than those required to elicit /sup 45/Ca/sup + +/ efflux. Equilibration of cultures with agonist prior to measurement of (/sup 3/H)prazosin binding resulted in small decreases in apparent agonist affinities. These results indicate that BC3H-1 cells possess a small ..cap alpha../sub 1/-receptor reserve for agonist-elicited /sup 45/Ca/sup + +/ efflux which is reflected in the catecholamine agonists, and that exposure to agonist converts receptors to a state of reduced agonist affinity.

• Research Organization: Univ. of California at San Diego, La Jolla
• OSTI ID: 7108457
• Report Number(s): CONF-8606151-
• Conference Information: Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Journal Volume: 45:6
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ADRENAL HORMONES
ADRENALINE
AFFINITY
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
AMINES
ANTIHYPERTENSIVE AGENTS
AROMATICS
AUTONOMIC NERVOUS SYSTEM AGENTS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
CALCIUM 45
CALCIUM COMPOUNDS
CALCIUM ISOTOPES
CARDIOTONICS
CARDIOVASCULAR AGENTS
CATECHOLAMINES
DAYS LIVING RADIOISOTOPES
DRUGS
EVEN-ODD NUCLEI
HORMONES
HYDROXY COMPOUNDS
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LABELLED COMPOUNDS
MEMBRANE PROTEINS
MEMBRANE TRANSPORT
MUSCLES
NEUROREGULATORS
NORADRENALINE
NUCLEI
ORGANIC COMPOUNDS
PHENOLS
POLYPHENOLS
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RECEPTORS
STEROID HORMONES
SYMPATHOMIMETICS
TRACER TECHNIQUES
TRITIUM COMPOUNDS