Biomaterial Database

The role of superficially bound calcium in the regulation of myocardial contractility and the positive inotropic response to ouabain. 1982

L E Bailey, and A B Fawzi

Positive inotropic effects induced in hearts by paired pacing and ouabain treatment were found to be dependent on the content of calcium in a superficial pool, Ca1. Two possible mechanisms for the expansion of this pool were investigated in isolated cardiac myocytes in which the cell surface structures were preserved from proteolytic digestion. Guinea pig ventricles were disrupted mechanically to obtain intact myocardial cells. The cell yield from this preparation was enriched by incubation with Cytodex beads and the characteristics of calcium binding to the cell-bed suspension were determined by continuous flow equilibrium dialysis. Scatchard plots revealed two components for calcium binding; a high affinity (Ka approximately 65 mM-1) and a low affinity (Ka approximately 140 M-1) pool. Ouabain (10(-9) to 10(-6)M) increased, in a dose related manner, the KA for calcium binding to the low affinity sites without affecting the total number of binding sites. The calculated amount of calcium bound to the low affinity pool at [Ca]e = 1.8 mM was closely correlated with the positive inotropic effect (PIE) measured in guinea pig hearts perfused with the same calcium concentration. At [Ca]e = 0.45, 0.9, or 3.6 mM, the response to ouabain (1 X 10(-7) and 5 X 10(-7)M) was greater than expected on the basis of the increase in calcium binding to the low affinity sites. The results suggest that at least one event in the inotropic response to ouabain involves increased affinity for calcium binding to low affinity sites on the cell surface, but that the increase in calcium bound at any [Ca]e is insufficient to produce the PIE directly.

UI	MeSH Term	Description	Entries
D007473	Ion Channels	Gated, ion-selective glycoproteins that traverse membranes. The stimulus for ION CHANNEL GATING can be due to a variety of stimuli such as LIGANDS, a TRANSMEMBRANE POTENTIAL DIFFERENCE, mechanical deformation or through INTRACELLULAR SIGNALING PEPTIDES AND PROTEINS.	Membrane Channels,Ion Channel,Ionic Channel,Ionic Channels,Membrane Channel,Channel, Ion,Channel, Ionic,Channel, Membrane,Channels, Ion,Channels, Ionic,Channels, Membrane
D008297	Male		Males
D009200	Myocardial Contraction	Contractile activity of the MYOCARDIUM.	Heart Contractility,Inotropism, Cardiac,Cardiac Inotropism,Cardiac Inotropisms,Contractilities, Heart,Contractility, Heart,Contraction, Myocardial,Contractions, Myocardial,Heart Contractilities,Inotropisms, Cardiac,Myocardial Contractions
D009206	Myocardium	The muscle tissue of the HEART. It is composed of striated, involuntary muscle cells (MYOCYTES, CARDIAC) connected to form the contractile pump to generate blood flow.	Muscle, Cardiac,Muscle, Heart,Cardiac Muscle,Myocardia,Cardiac Muscles,Heart Muscle,Heart Muscles,Muscles, Cardiac,Muscles, Heart
D010042	Ouabain	A cardioactive glycoside consisting of rhamnose and ouabagenin, obtained from the seeds of Strophanthus gratus and other plants of the Apocynaceae; used like DIGITALIS. It is commonly used in cell biological studies as an inhibitor of the NA(+)-K(+)-EXCHANGING ATPASE.	Acocantherin,G-Strophanthin,Acolongifloroside K,G Strophanthin
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D002415	Cats	The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)	Felis catus,Felis domesticus,Domestic Cats,Felis domestica,Felis sylvestris catus,Cat,Cat, Domestic,Cats, Domestic,Domestic Cat
D005260	Female		Females
D006168	Guinea Pigs	A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.	Cavia,Cavia porcellus,Guinea Pig,Pig, Guinea,Pigs, Guinea
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia