Biomaterial Database

Calcium-dependent electrical activity and contraction of voltage-clamped frog single muscle fibres. 1980

D Potreau, and G Raymond

1. The electrical and mechanical activities of isolated frog muscle fibres have been simultaneously recorded under conditions which allow the development of a calcium permeability (chloride-free solution containing 72 mM-calcium levulinate instead of 115 mM-NaCl). 2. Long-lasting calcium action potentials and large and sustained contraction occur without inhibition of the potassium permeability. 3. The relationship observed between the slow inward calcium current and the amplitude of the contraction, under voltage-clamp conditions, resembles that found between IBa and tension in frog skeletal muscle and between ICa and the contraction in frog heart. A part of the mechanical response which is not abolished by manganese seems to be potential-dependent. 4. Integration of the current traces shows that the threshold of the contraction occurs at [Ca]1 near to 2.10(-6) M and that the contractile proteins are fully activated at [Ca]1 near to 10(-4) M, values which are in good agreement with those proposed by other authors. 5. The minimum calcium influx necessary to induce a detectable contraction is close to 4.8 p-moles/cm2. This value is 10-20 times larger than the calcium influx measured during a normal action potential. 6. On detubulated fibres the calcium permeability fails to develop: this indicates that this current originates from the T-system. The close correspondence between ICa and the contraction, and between the time course of the contraction at the end of the depolarizing steps suggests that the potential of the tubular membrane is better clamped than in normal physiological conditions.

UI	MeSH Term	Description	Entries
D008345	Manganese	A trace element with atomic symbol Mn, atomic number 25, and atomic weight 54.94. It is concentrated in cell mitochondria, mostly in the pituitary gland, liver, pancreas, kidney, and bone, influences the synthesis of mucopolysaccharides, stimulates hepatic synthesis of cholesterol and fatty acids, and is a cofactor in many enzymes, including arginase and alkaline phosphatase in the liver. (From AMA Drug Evaluations Annual 1992, p2035)
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
D009119	Muscle Contraction	A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.	Inotropism,Muscular Contraction,Contraction, Muscle,Contraction, Muscular,Contractions, Muscle,Contractions, Muscular,Inotropisms,Muscle Contractions,Muscular Contractions
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D011895	Rana ridibunda	A species of the family Ranidae which occurs primarily in Europe and is used widely in biomedical research.
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
D002712	Chlorides	Inorganic compounds derived from hydrochloric acid that contain the Cl- ion.	Chloride,Chloride Ion Level,Ion Level, Chloride,Level, Chloride Ion
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
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