AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 6 1064-R1070, Copyright © 1986 by American Physiological Society
Mode of adrenergic and peptidergic inhibition of ion transport in flounder gill
M. S. Davis and T. J. Shuttleworth
The mechanisms of inhibition of branchial ion transport by epinephrine and
somatostatin were investigated in the isolated perfused gill preparation of
seawater-adapted flounder Platichthys flesus. The electrogenic
transepithelial potential recorded in gills perfused and bathed with
identical salines was stimulated by glucagon, forskolin, or a cyclic
adenosine 5' monophosphate (AMP) derivative, each administered at a
concentration identified in preliminary experiments as being submaximally
effective. The subsequent abilities of epinephrine and somatostatin to
inhibit the stimulated potential were found to be dependent on the site of
action of the stimulatory agent with respect to the formation of cyclic
AMP. Thus the maximal adrenergic or peptidergic inhibition of the potential
stimulated by exogenous cyclic AMP was significantly reduced compared with
the maximal inhibition of the potential stimulated by either forskolin or
glucagon. The data indicate dual modes of action by which epinephrine and
somatostatin achieve maximal inhibition of branchial ion transport; a
cyclic AMP-independent mechanism that is effective in the presence of
cyclic AMP and an additional mechanism to inhibit cyclic AMP synthesis.
