Biomaterial Database

The action of adrenaline on pace-maker activity in cardiac Purkinje fibres. 1978

I Cohen, and D Eisner, and D Noble

1. Adrenaline is known to shift the activation curve for iK2 (s infinite curve) in a positive direction on the voltage axis. This should cause an increase in the slope of diastolic depolarization, but cannot account for the experimentally observed increase in the maximum diastolic potential (MDP). 2. On application of adrenaline, in voltage clamp studies on short sheep cardiac Purkinje fibres there is a consistent 5-15 mV negative shift of the reversal potential for the pace-maker current, iK2. This shift is not reversed on application of the beta-blockers sotalol or propranolol, or on washout for up to one hour. 3. A computer simulation, including this effect of adrenaline, shows that it can shift the maximum diastolic potential in the hyperpolarizing or depolarizing direction depending on the initial value of [K+]o. In both cases it will add to the increase in rate caused by the positive shift of the activation curve for iK2 (the s infinite shift). 4. Studies of the effects of adrenaline on the MDP and rate in long sheep Purkinje fibres show a slower reversibility of the MDP than the rate, consistent with a slower reversal of the shift in the iK2 reversal potential than the shift in s infinite. 5. Possible mechanisms of the shift in reversal potential are discussed with respect to K+ balance in the intercellular clefts of the Purkinje fibre, including a a stimulation of the Na+- K+ pump. The possible sources of voltage clamp artifact are also discussed.

UI	MeSH Term	Description	Entries
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.
D011690	Purkinje Fibers	Modified cardiac muscle fibers composing the terminal portion of the heart conduction system.	Purkinje Fiber,Fiber, Purkinje,Fibers, Purkinje
D003201	Computers	Programmable electronic devices designed to accept data, perform prescribed mathematical and logical operations at high speed, and display the results of these operations.	Calculators, Programmable,Computer Hardware,Computers, Digital,Hardware, Computer,Calculator, Programmable,Computer,Computer, Digital,Digital Computer,Digital Computers,Programmable Calculator,Programmable Calculators
D003971	Diastole	Post-systolic relaxation of the HEART, especially the HEART VENTRICLES.	Diastoles
D004837	Epinephrine	The active sympathomimetic hormone from the ADRENAL MEDULLA. It stimulates both the alpha- and beta- adrenergic systems, causes systemic VASOCONSTRICTION and gastrointestinal relaxation, stimulates the HEART, and dilates BRONCHI and cerebral vessels. It is used in ASTHMA and CARDIAC FAILURE and to delay absorption of local ANESTHETICS.	Adrenaline,4-(1-Hydroxy-2-(methylamino)ethyl)-1,2-benzenediol,Adrenaline Acid Tartrate,Adrenaline Bitartrate,Adrenaline Hydrochloride,Epifrin,Epinephrine Acetate,Epinephrine Bitartrate,Epinephrine Hydrochloride,Epinephrine Hydrogen Tartrate,Epitrate,Lyophrin,Medihaler-Epi,Acetate, Epinephrine
D006329	Heart Conduction System	An impulse-conducting system composed of modified cardiac muscle, having the power of spontaneous rhythmicity and conduction more highly developed than the rest of the heart.	Conduction System, Heart,Conduction Systems, Heart,Heart Conduction Systems,System, Heart Conduction,Systems, Heart Conduction
D000200	Action Potentials	Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.	Spike Potentials,Nerve Impulses,Action Potential,Impulse, Nerve,Impulses, Nerve,Nerve Impulse,Potential, Action,Potential, Spike,Potentials, Action,Potentials, Spike,Spike Potential
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
D012756	Sheep	Any of the ruminant mammals with curved horns in the genus Ovis, family Bovidae. They possess lachrymal grooves and interdigital glands, which are absent in GOATS.	Ovis,Sheep, Dall,Dall Sheep,Ovis dalli
D066298	In Vitro Techniques	Methods to study reactions or processes taking place in an artificial environment outside the living organism.	In Vitro Test,In Vitro Testing,In Vitro Tests,In Vitro as Topic,In Vitro,In Vitro Technique,In Vitro Testings,Technique, In Vitro,Techniques, In Vitro,Test, In Vitro,Testing, In Vitro,Testings, In Vitro,Tests, In Vitro,Vitro Testing, In