Biomaterial Database

Effects of intracellular sodium and potassium iontophoresis on membrane potentials and resistances in toad urinary bladder. 1985

J Narvarte, and A L Finn

Glass microelectrodes were used to measure membrane potentials and the ratio of apical to basolateral membrane resistances before and after the passage of current from the potential-recording microelectrode to ground, in toad urinary bladder epithelium, in order to iontophorese cations into the cell. After application of the current, there was a transient change in the tip potential of the microelectrode. This artifact was measured with the microelectrode in the mucosal medium and was subtracted from the potential recorded in the cell. The serosal medium was bathed by Ringer's solution containing 51.5 mM K+ to minimize any current-induced increase of K+ in the unstirred layer. Under those conditions, both Na+ and K+ iontophoresis caused a significant hyperpolarization of basolateral membrane potential (Vcs) and a significant increase in the ratio of apical to basolateral membrane resistances (Ra/Rb). When bladders were exposed to amiloride in the mucosal solution, Na+ iontophoresis caused the basolateral membrane to hyperpolarize, but no significant changes were observed in Ra/Rb. When Na+ was injected in the presence of serosal ouabain, Vcs depolarized and Ra/Rb increased. K+ iontophoresis caused the basolateral membrane potential to hyperpolarize in the presence of ouabain but Ra/Rb did not change significantly. These results indicate that the Na+ pump in toad bladder is rheogenic, that apical Na+ conductance is sensitive to the cell levels of Na+ and K+ and that the basolateral membrane is K+ permeable.

UI	MeSH Term	Description	Entries
D007478	Iontophoresis	Therapeutic introduction of ions of soluble salts into tissues by means of electric current. In medical literature it is commonly used to indicate the process of increasing the penetration of drugs into surface tissues by the application of electric current. It has nothing to do with ION EXCHANGE; AIR IONIZATION nor PHONOPHORESIS, none of which requires current.	Iontophoreses
D008433	Mathematics	The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Mathematic
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
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.
D001743	Urinary Bladder	A musculomembranous sac along the URINARY TRACT. URINE flows from the KIDNEYS into the bladder via the ureters (URETER), and is held there until URINATION.	Bladder,Bladder Detrusor Muscle,Detrusor Urinae,Bladder Detrusor Muscles,Bladder, Urinary,Detrusor Muscle, Bladder,Detrusor Muscles, Bladder
D002024	Bufo marinus	A species of the true toads, Bufonidae, becoming fairly common in the southern United States and almost pantropical. The secretions from the skin glands of this species are very toxic to animals.	Rhinella marina,Toad, Giant,Toad, Marine,Giant Toad,Giant Toads,Marine Toad,Marine Toads,Toads, Giant,Toads, Marine
D004553	Electric Conductivity	The ability of a substrate to allow the passage of ELECTRONS.	Electrical Conductivity,Conductivity, Electric,Conductivity, Electrical
D004594	Electrophysiology	The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.
D000584	Amiloride	A pyrazine compound inhibiting SODIUM reabsorption through SODIUM CHANNELS in renal EPITHELIAL CELLS. This inhibition creates a negative potential in the luminal membranes of principal cells, located in the distal convoluted tubule and collecting duct. Negative potential reduces secretion of potassium and hydrogen ions. Amiloride is used in conjunction with DIURETICS to spare POTASSIUM loss. (From Gilman et al., Goodman and Gilman's The Pharmacological Basis of Therapeutics, 9th ed, p705)	Amidal,Amiduret Trom,Amiloberag,Amiloride Hydrochloride,Amiloride Hydrochloride, Anhydrous,Kaluril,Midamor,Midoride,Modamide,Anhydrous Amiloride Hydrochloride,Hydrochloride, Amiloride,Hydrochloride, Anhydrous Amiloride,Trom, Amiduret