Biomaterial Database

Calcium dependence of open and shut interval distributions from calcium-activated potassium channels in cultured rat muscle. 1983

K L Magleby, and B S Pallotta

The stochastic properties of single Ca-activated K channels in excised patches of surface membrane from cultured rat muscle cells were studied using the patch-clamp technique. The distribution of all open intervals was described by the sum of two exponential distributions of short and long mean open time, suggesting at least two major open-channel states. Increasing the concentration of Ca at the inner membrane surface, [Ca]i, increased the mean duration of the long open distribution, while having little effect on the mean duration of the short open distribution. The frequency of openings to each distribution increased with [Ca]i. The rate of increase was a much steeper function of [Ca]i for openings in the long open distribution than for openings in the short open distribution; about 80% of the openings were to the long open distribution with 0.1 microM-Cai, increasing to 97% with 1 microM-Cai (+ 30 mV). These results suggest that openings in both open distributions are Ca-dependent, with openings in the long open distribution requiring the binding of more Ca ions than openings in the short open distribution. The distribution of all shut intervals at 0.5 microM-Cai and + 30 mV was described by the sum of three exponential distributions with mean durations of: 0.21 msec (short shut distribution), 1.90 msec (intermediate shut), and 44 msec (long shut). These results indicate that the channel typically enters at least three closed channel states during normal channel activity. In addition, a few longer shut intervals not accounted for by the above distributions suggested that there was a fourth infrequently occurring inactivated closed-channel state. The mean duration of the distribution of long shut intervals decreased with a power of about 2 with increasing [Ca]i under conditions where most openings were to the long open state (+ 30 mV, 0.25-1 microM-Cai). This observation suggests that openings to the long open distribution typically require the binding of two or more Ca ions. The mean intermediate shut interval appeared to increase slightly with increasing [Ca]i while the mean short shut interval was relatively Cai-independent. The percentage of all shut intervals that were short shut intervals increased with increasing [Ca]i while the percentage of long shut intervals decreased.(ABSTRACT TRUNCATED AT 400 WORDS)

UI	MeSH Term	Description	Entries
D007473	Ion Channels	Gated, ion-selective glycoproteins that traverse membranes. The stimulus for ION CHANNEL GATING can be due to a variety of stimuli such as LIGANDS, a TRANSMEMBRANE POTENTIAL DIFFERENCE, mechanical deformation or through INTRACELLULAR SIGNALING PEPTIDES AND PROTEINS.	Membrane Channels,Ion Channel,Ionic Channel,Ionic Channels,Membrane Channel,Channel, Ion,Channel, Ionic,Channel, Membrane,Channels, Ion,Channels, Ionic,Channels, Membrane
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
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, 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.
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
D002462	Cell Membrane	The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.	Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D002478	Cells, Cultured	Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.	Cultured Cells,Cell, Cultured,Cultured Cell
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
D051381	Rats	The common name for the genus Rattus.	Rattus,Rats, Laboratory,Rats, Norway,Rattus norvegicus,Laboratory Rat,Laboratory Rats,Norway Rat,Norway Rats,Rat,Rat, Laboratory,Rat, Norway,norvegicus, Rattus