Two-phase positive inotropic effects of ouabain and the presence of multiple classes of ouabain binding sites in the ferret heart

Conference · Wed Mar 05 04:00:00 EST 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:7024741

Ng, Y C; Akera, T

Characteristics of more than one class of ouabain receptors which appear to exist in ferret heart were examined. In isolated papillary muscle, 1 to 30 nM ouabain produced a positive inotropic effect in the presence of 5 ..mu..M propranolol and 2 ..mu..M phentolamine. Higher concentrations of ouabain (0.1 to 10 ..mu..M) produced an additional and prominent inotropic effect. In partially purified Na, K-ATPase, ouabain caused a monophasic inhibition; however, the concentration-inhibition curve spanned over 5 log units, indicating that ouabain is interacting with more than a single class of the enzyme. Scatchard analysis of specific /sup 3/H-ouabain binding revealed approximately equal abundance of high and low affinity binding sites. The K/sub D/ value for high affinity sites was approximately 20 nM whereas that for low affinity sites was about 45 times higher. When phosphoenzyme was formed in the presence of (..gamma..-/sup 32/P)-ATP, Mg/sup 2 +/ and Na/sup +/ and subjected to SDS gel electrophoresis, two distinct K/sup +/-sensitive bands with about 100,000 dalton molecular weight were detected. Molecular weight difference between these two bands was approximately 2500 dalton. Phosphorylation of either band was abolished by 1 ..mu..M ouabain suggesting that both bands may correspond to the high-affinity binding sites. These results indicate that high and low affinity ouabain binding sites exists in approximately equal abundance in the ferret heart, and that binding of ouabain to these sites cases Na,K-ATPase inhibition and the positive inotropic effect.

• Research Organization: Michigan State Univ., East Lansing
• OSTI ID: 7024741
• Report Number(s): CONF-8604222-
• Conference Information: Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Journal Volume: 45:4
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ACID ANHYDRASES
AFFINITY
ANIMALS
ATP
ATP-ASE
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BODY
CARBOHYDRATES
CARDIAC GLYCOSIDES
CARDIOTONICS
CARDIOVASCULAR AGENTS
CARDIOVASCULAR SYSTEM
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
DRUGS
ENZYMES
GLYCOSIDES
HEART
HYDROLASES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LABELLED COMPOUNDS
LIGHT NUCLEI
MAMMALS
MEMBRANE PROTEINS
MUSCLES
NUCLEI
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANS
OUABAIN
PHOSPHOHYDROLASES
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
PHOSPHORYLATION
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RECEPTORS
STROPHANTHINS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES