Biomaterial Database

The role of electrogenic sodium pumping in the response of smooth muscle to acetylcholine. 1973

T B Bolton

1. Intracellular recording of membrane potential was made from the separated longitudinal muscle of the guinea-pig terminal ileum in physiological salt solution.2. When acetylcholine was washed from the tissue following a brief application the membrane repolarized and then hyperpolarized (;after-hyperpolarization') beyond the level existing before the application of acetylcholine.3. No after-hyperpolarization was observed following acetylcholine in potassium-free solution, in sodium-deficient (17 mM) solution, or in the presence of ouabain (1.7 x 10(-6)M). Repolarization under these conditions was delayed, especially after the membrane potential reached -20 to -30 mV, and was generally incomplete.4. The after-hyperpolarization was significantly (P < 0.01) greater when acetylcholine was applied in chloride-deficient (13 mM) solution.5. It was incidentally observed that the membrane potential in the presence of acetylcholine was more positive in potassium-free solution (significance P < 0.025), unchanged in chloride-deficient solution (P > 0.4), and much more negative in sodium-deficient (17 mM) solution (P << 0.001), confirming previous results using carbachol.6. When a 2 min application of 1.4 x 10(-6)M carbachol was made, the membrane potential 15-20 sec after beginning its application was not affected by ouabain (10(-5)M), but showed a significantly (P < 0.005) greater positive shift subsequently, so that the potential after 120 sec in carbachol was significantly (P < 0.025) more positive in the presence of ouabain. After 45 sec in 5.5 x 10(-5)M carbachol the membrane potential was also significantly (P < 0.005) more positive in the presence of ouabain (10(-5)M).7. Calculations based on hypotheses concerning the movements of sodium and potassium showed that the positive shift of the membrane potential in the presence of carbachol when sodium pumping was arrested, could be quantitatively explained by a decline in the sodium and potassium gradients across the membrane. It appeared that the electrogenic fraction of the sodium pumped was small in the presence of carbachol.8. It was concluded that the application of acetylcholine or carbachol (> 10(-6)M) to this smooth muscle disturbs the sodium and potassium gradients across the membrane. These disturbances are in a direction which stimulates electrogenic sodium pumping. Some limitation of depolarization results, and the increased electrogenic extrusion of sodium is responsible for the after-hyperpolarization which follows the application of acetylcholine.

UI	MeSH Term	Description	Entries
D007082	Ileum	The distal and narrowest portion of the SMALL INTESTINE, between the JEJUNUM and the ILEOCECAL VALVE of the LARGE INTESTINE.
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
D009130	Muscle, Smooth	Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. (From Stedman, 25th ed)	Muscle, Involuntary,Smooth Muscle,Involuntary Muscle,Involuntary Muscles,Muscles, Involuntary,Muscles, Smooth,Smooth Muscles
D010042	Ouabain	A cardioactive glycoside consisting of rhamnose and ouabagenin, obtained from the seeds of Strophanthus gratus and other plants of the Apocynaceae; used like DIGITALIS. It is commonly used in cell biological studies as an inhibitor of the NA(+)-K(+)-EXCHANGING ATPASE.	Acocantherin,G-Strophanthin,Acolongifloroside K,G Strophanthin
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.
D002217	Carbachol	A slowly hydrolyzed CHOLINERGIC AGONIST that acts at both MUSCARINIC RECEPTORS and NICOTINIC RECEPTORS.	Carbamylcholine,Carbacholine,Carbamann,Carbamoylcholine,Carbastat,Carbocholine,Carboptic,Doryl,Isopto Carbachol,Jestryl,Miostat,Carbachol, Isopto
D002712	Chlorides	Inorganic compounds derived from hydrochloric acid that contain the Cl- ion.	Chloride,Chloride Ion Level,Ion Level, Chloride,Level, Chloride Ion
D006168	Guinea Pigs	A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.	Cavia,Cavia porcellus,Guinea Pig,Pig, Guinea,Pigs, Guinea
D000109	Acetylcholine	A neurotransmitter found at neuromuscular junctions, autonomic ganglia, parasympathetic effector junctions, a subset of sympathetic effector junctions, and at many sites in the central nervous system.	2-(Acetyloxy)-N,N,N-trimethylethanaminium,Acetilcolina Cusi,Acetylcholine Bromide,Acetylcholine Chloride,Acetylcholine Fluoride,Acetylcholine Hydroxide,Acetylcholine Iodide,Acetylcholine L-Tartrate,Acetylcholine Perchlorate,Acetylcholine Picrate,Acetylcholine Picrate (1:1),Acetylcholine Sulfate (1:1),Bromoacetylcholine,Chloroacetylcholine,Miochol,Acetylcholine L Tartrate,Bromide, Acetylcholine,Cusi, Acetilcolina,Fluoride, Acetylcholine,Hydroxide, Acetylcholine,Iodide, Acetylcholine,L-Tartrate, Acetylcholine,Perchlorate, Acetylcholine
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