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When added to the mucosal solution bathing isolated frog skin at concentrations ranging from 5 X 10(-4) to 3 X 10(-3) M, the diuretic furosemide increased both the active transport of sodium and the electrical potential difference across the tissue in a dose-dependent way. The same effect was observed in chloride-free solutions. Mucosal furosemide also(More)
Open-tip and Cl−-selective microelectrodes were used to study the effect of external pH on apical membrane potential (V a) and intracellular chloride activity (a Cl i ) in epithelial cells ofNecturus gallbladder. Increasing the pH from 7.2 to 8.2 in the mucosal, the serosal, or in both bathing solutions simultaneously, hyperpolarizedV a (control value −60±5(More)
The effect of furosemide on acid secretion and Cl- transport was studied in isolated fundic mucosa of the guinea pig. Furosemide (10(-3) M), applied to the serosal side produced an immediate effect on the short-circuit current (Isc), lowering it by 47 +/- 2%. Potential difference decreased by 29 +/- 3%, electrical conductance by 18 +/- 4%, acid secretion by(More)
The formalism of nonequilibrium thermodynamics (NET) was used to analyze the effect of diuretic furosemide on the transport mechanism of frog skin. Mucosal furosemide increased the active conductance of Na+ across the mucosal membrane of the cells, producing an increased transport of Na+ (short-circuit current). Furosemide also increased both the(More)
Ouabain (10(-4) M) added to the serosal solution of isolated frog skin not only stops the active transport of Na+ but causes a dramatic increase in the electric conductance of the skin. The effect also appears when ouabain is added to amiloride-pretreated skins, ruling out the possibility of a cellular effect. The similarity between the effect of ouabain on(More)
1. Apical membrane potential (Va), transepithelial potential (VT), fractional apical voltage ratio (FVa = delta Va/delta VT), tissue resistance (RT), and intracellular Cl- (aiCl) and K+ (aiK) activities were measured in isolated gallbladders maintained between oxygenated bicarbonate-free physiological media (23 degrees C, pH 7.2 or 8.2) in a divided(More)
Enhanced cellular cAMP levels have been shown to increase apical membrane Cl− and HCO 3 − conductances in epithelia. We found that the phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine (IBMX) increases cAMP levels inNecturus gallbladder. We used conventional open-tip and double-barreled Cl−-selective microelectrodes to study the effects of IBMX on(More)
K+ and Cl−-selective double-barreled microelectrodes were used to study the effect of changes in external K+ concentration on intracellular Cl− activity (a Cl i ) in epithelial cells ofNecturus gallbladder. Decreasing the K+ concentration simultaneously in both bathing solutions produced a decrease ina Cl i . Steady-state values ofa Cl i were related to the(More)