AJP - Cell Physiology, Vol 266, Issue 4 C1069-C1076, Copyright © 1994 by American Physiological Society
Effect of brefeldin A on ADH-induced transport responses of toad bladder
K. Weng and J. B. Wade
Department of Physiology, University of Maryland at Baltimore, School of Medicine 21201.
We have used brefeldin A (BFA) to examine the role of membrane traffic in
the short-circuit current (ISC) and water permeability responses of the
toad urinary bladder. BFA treatment of 1 or 5 micrograms/ml had a complex
effect on the response of the ISC to antidiuretic hormone (ADH) or
forskolin stimulation. Although the responses to initial challenges by ADH
were not impaired by BFA, subsequent ISC responses were progressively
reduced. Similarly, while the response to an initial challenge by forskolin
was modestly reduced by BFA, subsequent responses were markedly reduced.
Inhibition of protein synthesis with cycloheximide (CHM) affected ISC
responses similarly. Neither BFA nor CHM had an effect on water
permeability responses. These observations show that although the membrane
traffic responsible for the water permeability response is insensitive to
inhibition by BFA or CHM, the stimulation of Na+ transport becomes
increasingly sensitive to these inhibitors with successive challenges by
ADH or forskolin. Although initial increases in Na+ transport utilize
preexisting components, subsequent responses appear to require an intact
system for membrane biogenesis.
