Biomaterial Database

Importance of magnesium and potassium concentration on basal tone and 5-HT-induced contractions in canine isolated coronary artery. 1988

T Murakawa, and B T Altura, and A Carella, and B M Altura

Department of Physiology, State University of New York, Brooklyn 11203.

1. In vitro studies were undertaken to investigate the effects of external potassium ([K+]o) and magnesium ([Mg2+]o) concentration on canine coronary arterial basal tone and on 5-hydroxytryptamine (5-HT)-induced contractions. 2. Acute withdrawal of, or reduction in, [K+]o produced relaxation of basal tone in isolated coronary arteries, whereas acute withdrawal (but not reduction) of [Mg2+]o produced contraction of these blood vessels. 3. The magnitude of coronary contraction obtained on withdrawal of [Mg2+]o was dependent upon the [K+]o; the higher the [K+]o, the greater the contraction. 4. The precise ratio of [K+]o/[Mg2+]o appeared to be important in dictating the degree of contraction (maximum response) and sensitivity (EC50) of canine coronary vascular smooth muscle cells to 5-HT. The EC50 to 5-HT was enhanced by increases in the [K+]o/[Mg2+]o ratio, whereas the ability of 5-HT to induce a maximal contraction was attenuated by decreases in the [K+]o; the latter being modulated by [Mg2+]o. Small changes in [Mg2+]o could effect large changes in the EC50 as [K+]o was lowered. 5. These actions took place over patho-physiological ranges of [K+]o and [Mg2+]o. 6. Maintenance of a constant [K+]o/[Mg2+]o ratio, irrespective of the exact [K+]o and [Mg2+]o, produced similar degrees of maximum tension. 7. Use of intact vascular ring preparations and helically-cut vascular strips produced similar results with varying [K+]o/[Mg2+]o. 8. A variety of pharmacological receptor antagonists (phentolamine, propranolol, atropine, diphenhydramine, cimetidine), as well as a prostaglandin cyclo-oxygenase inhibitor, did not modify the altered contractile responses or basal tone evoked by varying [K+]o/[Mg2+]o ratios. 9. These results suggest: (1) that basal tone and contractility of canine coronary vascular smooth muscle cells appear to be exquisitely sensitive to alterations in extracellular K+ and Mg2+; and (2) 5-HT receptor-operated Ca2+ channels, as well as those Ca2+ channels involved in generation of coronary arterial basal tone are modulated and controlled by the precise concentrations of [K+]o and [Mg2+]o.

UI	MeSH Term	Description	Entries
D008274	Magnesium	A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.
D008297	Male		Males
D009129	Muscle Tonus	The state of activity or tension of a muscle beyond that related to its physical properties, that is, its active resistance to stretch. In skeletal muscle, tonus is dependent upon efferent innervation. (Stedman, 25th ed)	Muscle Tension,Muscle Tightness,Muscular Tension,Tension, Muscle,Tension, Muscular,Tightness, Muscle,Tonus, Muscle
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D003331	Coronary Vessels	The veins and arteries of the HEART.	Coronary Arteries,Sinus Node Artery,Coronary Veins,Arteries, Coronary,Arteries, Sinus Node,Artery, Coronary,Artery, Sinus Node,Coronary Artery,Coronary Vein,Coronary Vessel,Sinus Node Arteries,Vein, Coronary,Veins, Coronary,Vessel, Coronary,Vessels, Coronary
D004285	Dogs	The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)	Canis familiaris,Dog
D005260	Female		Females
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
D012701	Serotonin	A biochemical messenger and regulator, synthesized from the essential amino acid L-TRYPTOPHAN. In humans it is found primarily in the central nervous system, gastrointestinal tract, and blood platelets. Serotonin mediates several important physiological functions including neurotransmission, gastrointestinal motility, hemostasis, and cardiovascular integrity. Multiple receptor families (RECEPTORS, SEROTONIN) explain the broad physiological actions and distribution of this biochemical mediator.	5-HT,5-Hydroxytryptamine,3-(2-Aminoethyl)-1H-indol-5-ol,Enteramine,Hippophaine,Hydroxytryptamine,5 Hydroxytryptamine
D014661	Vasoconstriction	The physiological narrowing of BLOOD VESSELS by contraction of the VASCULAR SMOOTH MUSCLE.	Vasoconstrictions