Biomaterial Database

Ca2+-sensitive, spontaneously fluctuating, cation channels in the apical membrane of the adult frog skin epithelium. 1985

W Van Driessche, and W Zeiske

The fluctuations in transepithelial current through the abdominal skin of bullfrogs (Rana catesbeiana) were analysed while the transepithelial voltage was clamped to zero. A Lorentzian component in the power spectrum was recorded when the skin was bathed with Ca2+ free NaCl Ringer's on both sides. After replacement of all mucosal Na+ by choline the Lorentzian component disappeared. The application of mucosa positive potentials enhanced the plateau of the relaxation noise component while it was depressed by mucosa negative potentials. These observations showed that the current associated with the relaxation noise, was carried by Na+ moving in the inward direction. Divalent cations added to the mucosal solution in micromolar concentrations depressed the relaxation noise immediately, which is indicative for an apical localization of the fluctuating channels. The relaxation noise depended strongly on the pH of the mucosal medium: alkalinization enhanced the relaxation noise while acidification depressed the fluctuations. Micromolar concentrations of the diuretic amiloride, which is known to block the Na+ entry into the cellular compartment, enhanced the Na+-dependent relaxation noise while at higher concentrations an inhibitory effect was observed. From these observations it was concluded that the relaxation noise is caused by inward Na+ movement through fluctuating channels which are localized in the apical membrane. These channels seem to constitute a pathway in parallel with the amiloride-blockable channels. Ionic substitution of Na+ by other monovalent cations showed that these channels are also permeable for K+, Rb+, NH4+, Cs+ and Tl+, but not for Li+. Divalent cations in micromolar concentrations completely occlude these fluctuating channels. Therefore, this pathway will be blocked for monovalent cations when normal Ca2+ containing Ringer's are used as mucosal bathing medium.

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
D008566	Membranes	Thin layers of tissue which cover parts of the body, separate adjacent cavities, or connect adjacent structures.	Membrane Tissue,Membrane,Membrane Tissues,Tissue, Membrane,Tissues, Membrane
D009092	Mucous Membrane	An EPITHELIUM with MUCUS-secreting cells, such as GOBLET CELLS. It forms the lining of many body cavities, such as the DIGESTIVE TRACT, the RESPIRATORY TRACT, and the reproductive tract. Mucosa, rich in blood and lymph vessels, comprises an inner epithelium, a middle layer (lamina propria) of loose CONNECTIVE TISSUE, and an outer layer (muscularis mucosae) of SMOOTH MUSCLE CELLS that separates the mucosa from submucosa.	Lamina Propria,Mucosa,Mucosal Tissue,Muscularis Mucosae,Mucous Membranes,Membrane, Mucous,Membranes, Mucous,Mucosae, Muscularis,Mucosal Tissues,Propria, Lamina,Tissue, Mucosal,Tissues, Mucosal
D011892	Rana catesbeiana	A species of the family Ranidae (true frogs). The only anuran properly referred to by the common name "bullfrog", it is the largest native anuran in North America.	Bullfrog,Bullfrogs,Rana catesbeianas,catesbeiana, Rana
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
D002412	Cations	Positively charged atoms, radicals or groups of atoms which travel to the cathode or negative pole during electrolysis.	Cation
D002413	Cations, Divalent	Positively charged atoms, radicals or groups of atoms with a valence of plus 2, which travel to the cathode or negative pole during electrolysis.	Divalent Cations
D004560	Electricity	The physical effects involving the presence of electric charges at rest and in motion.
D004848	Epithelium	The layers of EPITHELIAL CELLS which cover the inner and outer surfaces of the cutaneous, mucus, and serous tissues and glands of the body.	Mesothelium,Epithelial Tissue,Mesothelial Tissue,Epithelial Tissues,Mesothelial Tissues,Tissue, Epithelial,Tissue, Mesothelial,Tissues, Epithelial,Tissues, Mesothelial
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