Biomaterial Database

Reprimed charge movement in skeletal muscle fibres. 1978

R F Rakowski

1. The three intracellular micro-electrode voltage-clamp technique was used to study the recovery of membrane charge movement in semitendinosus muscles of Rana pipiens. Muscles were placed in a hypertonic depolarizing solution to inactivate voltage dependent charge movement. Tetrodotoxin and tetraethylammonium ions (TEA+) were present to block voltage dependent ionic conductances. Rb+ and SO4(2-) were present to reduce inward rectification and leakage conductance. 2. The recovery ('repriming') of membrane charge movement was studied following hyperpolarizing pulses from a holding potential of -20 mV to membrane potentials from -30 to -140 mV for durations of 2--100 sec. The reprimed charge movement measured as the difference in membrane current required for identical voltage steps before and after long duration hyperpolarizing pulses was a linear function of membrane potential and symmetrical in shape. Reprimed charge is, therefore, simply the result of an increase in the linear capacitance of the fibre. 3. The mean value of the percent increase in capacitance for repriming at -100 mV was 12.3 +/- 1.7% (S.E. of mean) for 25 sec duration pulses and 27.8 +/- 2.9% for 100 sec duration pulses. If these data are corrected to the steady state and the surface contribution subtracted, the mean increase in 'volume' capacity is 40.3 +/- 3.6% (n = 21) for fibres with a mean diameter of 51 +/- 4 micron. 4. The increase in capacity can arise either by an increase in the transverse tubular length constant (lambdaT) or by gaining electrical access to additional linear capacitance within the fibre volume. If the capacitance arises solely from the transverse tubular system, the value of lambdaT before repriming can be no larger than 20 micron in order to explain the observed increase in volume capacity. A value of lambdaT as small as this seems unlikely. 5. The observation that reprimed charge is simply the result of an increase in linear capacitance is not consistent with the hypothesis that it is a gating mechanism for the activation of contraction.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
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
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D011894	Rana pipiens	A highly variable species of the family Ranidae in Canada, the United States and Central America. It is the most widely used Anuran in biomedical research.	Frog, Leopard,Leopard Frog,Lithobates pipiens,Frogs, Leopard,Leopard Frogs
D004553	Electric Conductivity	The ability of a substrate to allow the passage of ELECTRONS.	Electrical Conductivity,Conductivity, Electric,Conductivity, Electrical
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
D001001	Anura	An order of the class Amphibia, which includes several families of frogs and toads. They are characterized by well developed hind limbs adapted for jumping, fused head and trunk and webbed toes. The term "toad" is ambiguous and is properly applied only to the family Bufonidae.	Bombina,Frogs and Toads,Salientia,Toad, Fire-Bellied,Toads and Frogs,Anuras,Fire-Bellied Toad,Fire-Bellied Toads,Salientias,Toad, Fire Bellied,Toads, Fire-Bellied
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