Inotropic effect, binding properties, and calcium flux effects of the calcium channel agonist CGP 28392 in intact cultured embryonic chick ventricular cells

Journal Article · Wed May 01 04:00:00 EDT 1985 · Circ. Res.; (United States)

DOI:https://doi.org/10.1161/01.RES.56.5.676· OSTI ID:5127022

Laurent, S; Kim, D; Smith, T W; Marsh, J D

CGP 28392 is a recently described dihydropyridine derivative with positive inotropic properties. To study the mechanism of action of this putative calcium channel agonist, we have related the effects of CGP 28392 on contraction (measured with an optical video system) and radioactive calcium uptake to ligand-binding studies in cultured, spontaneously beating chick embryo ventricular cells. CGP 28392 produced a concentration-dependent increase in amplitude and velocity of contraction (EC/sub 50/ = 2 x 10(-7) M; maximum contractile effect = 85% of the calcium 3.6 mM response). Nifedipine produced a shift to the right of the concentration-effect curve for CGP 28392 without decreasing the maximum contractile response, suggesting competitive antagonism (pA2 = 8.3). Computer analysis of displacement of (/sup 3/H)nitrendipine binding to intact heart cells by unlabeled CGP 28392 indicated a K /sub D/ = 2.2 +/- 0.95 x 10(-7) M, in good agreement with the EC/sub 50/ for the inotropic effect. CGP 28392 increased the rate of radioactive calcium influx (+39% at 10 seconds) without altering beating rate, while nifedipine decreased radioactive calcium influx and antagonized the CGP 28392-induced increase in calcium influx. Our results indicate that, in intact cultured myocytes, CGP 28392 acts as a calcium channel agonist and competes for the dihydropyridine-binding site of the slow calcium channel. In contrast to calcium channel blockers, CGP 28392 increases calcium influx and enhances the contractile state.

• OSTI ID: 5127022
• Journal Information: Circ. Res.; (United States), Journal Name: Circ. Res.; (United States) Vol. 5; ISSN CIRUA
• Country of Publication: United States
• Language: English

Related Subjects

550501* -- Metabolism-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
ANIMAL CELLS
ANIMALS
AZINES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL EFFECTS
BIRDS
BODY
CALCIUM
CALCIUM ISOTOPES
CARDIOVASCULAR SYSTEM
CELL CULTURES
CHICKENS
DOSE-RESPONSE RELATIONSHIPS
ELEMENTS
EMBRYONIC CELLS
ENZYME INHIBITORS
FOWL
HEART
HETEROCYCLIC COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LABELLED COMPOUNDS
MEMBRANE PORES
MEMBRANE TRANSPORT
METALS
MUSCLES
MYOCARDIUM
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PYRIDINES
REACTION KINETICS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES