ISSN:
1432-2013
Keywords:
Water transport
;
Toad skin
;
Potassium depolarization
;
Cyclic AMP
;
Vasopressin
;
Isoproterenol
;
Intramembrane particle aggregates
;
Freeze-fracture
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Exposure of the inner surface of toad skin (Bufo marinus) to high [K+] resulted in a marked (up to 7-fold) increase in water permeability (P f) that was more marked in KCl-Ringer than in K2SO4-Ringer. Although high [K+] did not clicit a maximal increase inP f, it blunted the hydrosmotic responses to vasopressin, isoproterenol and cAMP. Both “post-cAMP” inhibitors of stimulated water flow, such as diamide and vanadate, and “pre-cAMP” inhibitors, such as methohexital and propranolol, markedly reduced the K response, while exposure to Ca2+-free, KCl-Ringer did not inhibit water flow. Intramembrane particle aggregates, similar to those induced by cAMP-mediated hydrosmotic agents, were seen in the apical membrane of granular cells, just beneath thestratum corneum, in skins exposed to KCl. Available evidence indicates that cAMP might mediate, at least partially, the hydrosmotic effect of high [K+]. In contrast, a role of voltage-dependent Ca2+ channels, described in other cell systems depolarized with K, was not apparent in toad skin.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00584728
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