Stanley Y. Loo

Effect of silver chloride on the short-circuit current across the isolated toad skin

Abstract Since addition of 10 −4 M AgNO 3 to either an inside or outside bathing medium containing sulfate had no effect on short-circuit current (SCC), a measure of net Na + transport, or transmural potential difference (PD) in the isolated surviving toadskin, the effect of adding Ag + to chloridebased Ringer solution was studied. Exposure of the outside bathing medium to 10 −4 M AgNO 3 resulted in, after a 20 minute time lag, a 250 ± 51% (N=6) increase in SCC within 100 minutes as opposed to an immediate response which had a 350 ± 26% (N=8) increase in SCC by addition of 10 −4 M AgNO 3 to the inside bathing solution. The dose response curve relating change in SCC to the Ag + concentration added to the inside bathing medium was saturable at 10 −5 M Ag + . The uptake of Ag + by the tissue, as measured by atomic absorption spectrophotometry, showed no correlation to the relative change in SCC. Na + flux experiments under short-circuited conditions showed that Ag + Cl − stimulated only the unidirectional outside to inside Na + flux. These results indicate that Ag + Cl − enhances active sodium transport and that Ag + Cl − binding to specific membrane groups is required for this effect.

Drug modification of silver-induced sodium transport across toad skin

Stimulation of active Na+ transport in the toad skin by antidiuretic hormone (ADH) and p-chloromecuribenzoate (P-CMB) was blunted by the presence of silver (Ag+). Amiloride inhibited active Na+ transport, equivalently, whether Ag+ was present or not.

Effect of silver on sodium transport across toad skin

Silver attenuated the insulin-induced short-circuit current and transmural potential difference. Silver diminished the ethacrynic acid-induced short-circuit current and transmural potential difference. Ouabain inhibited short-circuit current and transmural potential difference, equivalently, whether silver was present or not. The low concentration silver-induced short-circuit current is carried by a net active sodium transfer from the outside to the inside bathing solution.

Interactive effects of ethanol and silver on sodium transport across toad skin

Abstract Both ethanol and silver ions have been shown to affect ion transport across various epithelia. This investigation was principally undertaken to further define mechanisms of silver ions and ethanol, and their possible interactions, on sodium transport across toad skin. Isolated toad skin, mounted between identical oxygenated amphibian bicarbonate Ringer solutions, maintained stable transepithelial potential differences (serosa positive) and short-circuit currents for several hours at 25°C. It was observed that (1) ethanol inhibited the active transcellular component of sodium absorption and this effect was reversible; (2) inhibition of sodium transport by ethanol was directly proportional to the applied concentration; (3) pretreatment with silver ions prevented any ethanol effects; and (4) pretreatment with ethanol prevented any silver ion effects. It was concluded from these results that ethanol induced its inhibitory effects on membrane phospholipids thereby perturbing the function of a sulfhydryl ligand, while silver ion or silver chloride complex binding to this ligand would maintain its function in sodium transport despite the presence of ethanol.

Ethanol and silver effects on ion transport across toad skin

Silver stimulated short-circuit current and transepithelial potential difference. Ethanol inhibited transpithelial potential difference. Ethanol had no effect on short-circuit current. Ethanol stimulated unidirectional movements of chloride from outside to inside and from inside to outside.

Modification of silver-enhanced sodium transport across toad skin

1. Silver stimulated short-circuit current and transepithelial potential difference. 2. Cysteine inhibited the silver-induced short-circuit current. 3. There was a dose-response inhibition of silver-induced short-circuit current by cysteine. 4. The silver-induced short-circuit current is carried by a net active sodium transfer from the outside to the inside bathing solution.

N-ethylmaleimide inhibition of silver-enhanced sodium transport across toad (Bufo macinus) skin.

1. Silver stimulated short-circuit current and transepithelial potential difference. 2. N-Ethylmaleimide inhibited the silver-induced short-circuit current. 3. There was a biphasic inhibition of silver-induced short-circuit current by N-ethylmaleimide. 4. There is a specific, maximal number of sulfhydryl groups associated with active sodium absorption. 5. Stimulation of active sodium transport by antidiuretic hormone was blunted by the presence of silver. 6. The silver-induced short-circuit current is carried by a net active sodium transfer from the outside to the inside bathing solution.

Effect of laticauda semifasciata (sea snake) venom on sodium transport across the frog skin

Abstract 1. 1. Addition of Laticauda semifasciata venom to the outside bathing solution of isolated frog skin elicited sustained increases in transmural potential difference, short-circuit current and transmural electrical resistance. 2. 2. Addition of Laticauda semifasciata venom to human red cell ghosts had no effect on Na+-K+-dependent ATPase activity. 3. 3. The Laticauda semifasciata venom-induced short-circuit current is carried by a net active sodium transfer from the outside to the inside bathing solution.

Transport energetics of the Na+ pump in Aplysia californica gut

Basolateral membranes of Aplysia californica foregut epithelia contain an ATP-dependent Na+ transporter (Na+ pump). Increased activity of the Na+ pump, coupled to luminal Na+/AIB symporter activity and basolateral membrane depolarization, changed the Na+ transport energetics across the basolateral membrane to a greater extent than the change in Na+ transport energetics across the luminal membrane.