β-Cyclodextrin and permeability to water in the bladder of Bufo arenarum.

We measured the effect of β-cyclodextrin (BCD, a cholesterol scavenger) on water flow across the isolated toad bladder exposed to an osmotic gradient (J(w)) by a gravimetric technique. BCD, when present in the solution bathing the apical side of the bladder, inhibited the increase in J(w) caused by nystatin, a polyene antibiotic that acts by directly binding apical membrane cholesterol. When present in the basolateral bath, BCD inhibited the increase in J(w) caused by basolateral exposure to oxytocin (which binds membrane receptors and stimulates the synthesis of cAMP), but did not alter the response to theophylline (which inhibits hydrolysis of cAMP by cyclic nucleotide phosphodiesterase).

Effect of mercuric chloride on electrical parameters and anion fluxes in the toad skin.

The amphibian skin, widely used for studying the transepithelial passage of electrolytes, exhibits anion pathways relatively specific for Cl(-). We studied the effect of HgCl(2), 1.0 x 10(-4) M on its electrical parameters and unidirectional anion fluxes.

Permeability to water in a tight epithelium: possible modulating action of gap junctions.

Osmotic water flow (Jw) across tight distal nephron epithelial membranes increases upon exposure to vasopressin: following binding of the hormone to its receptors, intracellular cyclic AMP concentration increases, leading to insertion of aquaporins in the apical membrane. The involvement of intercellular communication in the process, however, has not been adequately explored. Octanol, 1.