Biomaterial Database

Effect of strophanthidin on intracellular Na ion activity and twitch tension of constantly driven canine cardiac Purkinje fibers. 1982

C O Lee, and M Dagostino

Intracellular Na ion activity (aiNa) and twitch tension (T) of constantly driven (1 Hz) canine cardiac Purkinje fibers were measured simultaneously and continuously with neutral carrier Na+-selective microelectrodes and a force transducer. The aiNa of 8.9 +/- 1.4 mM (mean +/- SD, n = 52) was obtained in the driven fibers perfused with normal Tyrode solution. Temporary interruption of stimulation showed that aiNa of the driven fibers was approximately 1.5 mM greater than that of quiescent fibers. The constantly driven fibers were exposed to strophanthidin of 10(-8), 5 X 10(-8), 10(-7), 5 X 10(-7), and 10(-6) M for 5 min. No detectable changes in aiNa and T were observed in the fibers exposed to 10(-8) M strophanthidin, and the threshold concentration of the strophanthidin effect appeared to be approximately 5 X 10(-8) M. With concentrations greater than 5 X 10(-8) M, strophanthidin produced dose-dependent increases in aiNa and T. An increase in aiNa always accompanied an increase in T and after strophanthidin exposure both aiNa and T recovered completely. During onset and recovery periods of the strophanthidin effect the time course of change in aiNa was similar to that of change in T. A plot of T vs. aiNa during the onset and recovery periods showed a linear relationship between T and aiNa. These results indicate strongly that the positive inotropic effect of strophanthidin is closely associated with the increase in aiNa. Raising [K+]0 from 5.4 to 10.8 mM produced decreases in aiNa and T, and restoration of [K+]0 resulted in recoveries of aiNa and T. During the changes of [K+]0 the time course of change in aiNa was similar to that of the change in T. A steady-state sarcoplasmic Ca ion activity (aiCa) of 112 +/- 31 nM (mean +/- SD, n = 17) was obtained in the driven fibers with the use of neutral carrier Ca2+-selective microelectrodes. Temporary interruption produced 10-30% decreases in aiCa. No detectable changes in aiCa were observed in the fibers exposed to strophanthidin of 10(-7) M or less; 5 X 10(-7) and 10(-6) M strophanthidin produced 1.3-1.6 and 2-3-fold increases in aiCa, respectively. This result is consistent with the hypothesis that an increase in aiNa produces an increase in aiCa, which enhances Ca accumulation in the intracellular stores.

UI	MeSH Term	Description	Entries
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D011690	Purkinje Fibers	Modified cardiac muscle fibers composing the terminal portion of the heart conduction system.	Purkinje Fiber,Fiber, Purkinje,Fibers, Purkinje
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
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
D004553	Electric Conductivity	The ability of a substrate to allow the passage of ELECTRONS.	Electrical Conductivity,Conductivity, Electric,Conductivity, Electrical
D006321	Heart	The hollow, muscular organ that maintains the circulation of the blood.	Hearts
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
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
D012519	Sarcoplasmic Reticulum	A network of tubules and sacs in the cytoplasm of SKELETAL MUSCLE FIBERS that assist with muscle contraction and relaxation by releasing and storing calcium ions.	Reticulum, Sarcoplasmic,Reticulums, Sarcoplasmic,Sarcoplasmic Reticulums
D012964	Sodium	A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.	Sodium Ion Level,Sodium-23,Ion Level, Sodium,Level, Sodium Ion,Sodium 23