Effects of prolonged saline exposure on water, sodium and urea transport and on electron‐microscopical characteristics of the isolated urinary bladder of the toad Bufo bufo

Open Access
Publisher Website
Google Scholar
Abstract
1. A comparison was made of various transport properties and electron‐microscopical characteristics of isolated urinary bladders from toads (Bufo bufo) maintained in either tap water or 0·7% saline (0·7 g NaCl in 100 ml. H2O) for 10 days to 2 months. 2. In the absence of Pitressin, isolated bladders from saline‐adapted toads showed: (a) markedly, and significantly, lower osmotic water flow; (b) moderately, but not significantly, lower urea permeability; (c) no significant change in net sodium transport (measured as short‐circuit current, Isc); and (d) significantly smaller intercellular space/mucosal cell ratios in electron‐micrographs. 3. Differences in the transport and electron‐microscopical characteristics between bladders from water‐exposed and saline‐adapted toads became more evident in the presence of exogenous Pitressin (10 m‐u./ml. serosal solution): (a) the stimulating influence of Pitressin on osmotic water flow, short‐circuit current and urea permeability was considerably smaller in bladders from saline‐adapted toads than in those from water‐exposed toads; (b) the influence of Pitressin on short‐circuit current was reduced more profoundly than that on either water flow or urea permeability; (c) the Pitressin‐induced increment in intercellular space/mucosal cell ratio was significantly smaller in electron‐micrographs of bladders from saline‐adapted toads than in those from water exposed toads. 4. The effects of saline adaptation are discussed in relation to decreased permeability of mucosal membrane barriers.