Biomaterial Database

Effect of frusemide, ethacrynic acid and indanyloxyacetic acid on spontaneous Ca-activated currents in rabbit portal vein smooth muscle cells. 1995

I A Greenwood, and R C Hogg, and W A Large

Department of Pharmacology and Clinical Pharmacology, St. George's Hospital Medical School, London.

1. The effect of frusemide, ethacrynic acid and indanyloxyacetic acid was investigated on spontaneous calcium-activated chloride (ICl(Ca)) and potassium currents (IK(Ca)) in rabbit portal vein cells with the perforated patch technique. 2. Frusemide (0.3-1.0 x 10(-3) M) reduced the amplitude of spontaneous transient inward chloride currents (STICs) in a concentration-dependent manner. The degree of inhibition on STIC amplitude was similar between -50 and +30 mV and frusemide did not alter the STIC reversal potential (Erev). 3. The voltage-dependent exponential decay of STICs, which is thought to represent closure of chloride channels, was not altered by frusemide. 4. The amplitude and frequency of spontaneous potassium outward currents (STOCs) were not altered by frusemide. Since both STICs and STOCs are activated by calcium released from intracellular stores these data indicate that frusemide may block directly ICl(Ca). 5. Ethacrynic acid (2-5 x 10(-4) M) decreased the amplitude of STICs in a concentration-dependent manner by a similar amount at potentials of -50 to +30 mV but did not alter the STIC Erev. However, these concentrations of ethacrynic acid also reduced STOC amplitude and 5 x 10(-4) M ethacrynic acid evoked a sustained outward current in most cells at 0 mV; thus ethacrynic acid has a more complex action than simple block of ICl(Ca). 6. Indanyloxyacetic acid reduced both STIC amplitude and decay time without affecting STOCs and thus also seems to inhibit directly ICl(Ca). It is discussed whether block of ICl(Ca) mediates the vasodilator effect of these agents.

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
D009126	Muscle Relaxation	That phase of a muscle twitch during which a muscle returns to a resting position.	Muscle Relaxations,Relaxation, Muscle,Relaxations, Muscle
D009131	Muscle, Smooth, Vascular	The nonstriated involuntary muscle tissue of blood vessels.	Vascular Smooth Muscle,Muscle, Vascular Smooth,Muscles, Vascular Smooth,Smooth Muscle, Vascular,Smooth Muscles, Vascular,Vascular Smooth Muscles
D011169	Portal Vein	A short thick vein formed by union of the superior mesenteric vein and the splenic vein.	Portal Veins,Vein, Portal,Veins, Portal
D011817	Rabbits	A burrowing plant-eating mammal with hind limbs that are longer than its fore limbs. It belongs to the family Leporidae of the order Lagomorpha, and in contrast to hares, possesses 22 instead of 24 pairs of chromosomes.	Belgian Hare,New Zealand Rabbit,New Zealand Rabbits,New Zealand White Rabbit,Rabbit,Rabbit, Domestic,Chinchilla Rabbits,NZW Rabbits,New Zealand White Rabbits,Oryctolagus cuniculus,Chinchilla Rabbit,Domestic Rabbit,Domestic Rabbits,Hare, Belgian,NZW Rabbit,Rabbit, Chinchilla,Rabbit, NZW,Rabbit, New Zealand,Rabbits, Chinchilla,Rabbits, Domestic,Rabbits, NZW,Rabbits, New Zealand,Zealand Rabbit, New,Zealand Rabbits, New,cuniculus, Oryctolagus
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
D004232	Diuretics	Agents that promote the excretion of urine through their effects on kidney function.	Diuretic,Diuretic Effect,Diuretic Effects,Effect, Diuretic,Effects, Diuretic
D004976	Ethacrynic Acid	A compound that inhibits symport of sodium, potassium, and chloride primarily in the ascending limb of Henle, but also in the proximal and distal tubules. This pharmacological action results in excretion of these ions, increased urinary output, and reduction in extracellular fluid. This compound has been classified as a loop or high ceiling diuretic.	Edecrin,Etacrynic Acid,Ethacrinic Acid,Ethacrynate Sodium,Ethacrynic Acid, Sodium Salt,Hydromedin,Acid, Etacrynic,Acid, Ethacrinic,Acid, Ethacrynic,Sodium, Ethacrynate
D005260	Female		Females