Biomaterial Database

Characterization of the ionic mechanism responsible for the hyperpolarization-activated current in frog sinus venosus. 1987

G Champigny, and P Bois, and J Lenfant

Laboratoire de Physiologie Générale, U.A. CNRS no. 290, Faculté des Sciences, Université de Poitiers, France.

Voltage clamp experiments were carried out on the sinus venosus of the frog by means of the double mannitol gap technique. The ionic mechanism underlying the slowly hyperpolarization-activated inward current was investigated by changing the concentration and species of alkali cations and divalent cations in the bathing solution. Adding Rb or Cs in concentration of 10-20 mM to the control solution led to a dose-dependent increase in the inward current, as does elevating the external concentration of K from 2.5 to 25 mM. After the inward current had been nearly suppressed by completely substituting Tris for Na in the external medium, it was partially restored after a subsequent addition of K, Rb or Cs to the Na-free medium. Various alkaline earths or transition metals added to the bathing solution markedly depressed the magnitude of the inward current. This inhibitory effect varied with concentration and nature of divalent cations added. It also depended on the concentration and species of alkali cations present in the external solution. From these observations it was proposed that the conductance responsible for the inward rectification in frog sinus venosus does not discriminate among monovalent cations. The results support the existence of a weak-field-strength site located in the permeation pathway. Divalent cation may exert their inhibitory effect by competing with permeant ions for this site.

UI	MeSH Term	Description	Entries
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
D008672	Metals, Alkali	Metals that constitute group 1(formerly group IA) of the periodic table. They are the most strongly electropositive of the metals. Note that HYDROGEN is not considered an alkali metal even though it falls under the group 1 heading in the periodic table.	Alkali Metal,Alkali Metals,Group 1 Element,Group 1 Elements,1 Element, Group,Element, Group 1,Elements, Group 1,Metal, Alkali
D011893	Rana esculenta	An edible species of the family Ranidae, occurring in Europe and used extensively in biomedical research. Commonly referred to as "edible frog".	Pelophylax esculentus
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
D002414	Cations, Monovalent	Positively charged atoms, radicals or group of atoms with a valence of plus 1, which travel to the cathode or negative pole during electrolysis.	Monovalent Cation,Cation, Monovalent,Monovalent Cations
D006321	Heart	The hollow, muscular organ that maintains the circulation of the blood.	Hearts
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
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