AJP - Regulatory, Integrative and Comparative Physiology, Vol 232, Issue 3 110-R115, Copyright © 1977 by American Physiological Society
Epinephrine effects on branchial water and urea flux in rainbow trout
G. P. Haywood, J. Isaia and J. Maetz
In isolated trout heads, perfused at constant pressure, epinephrine (10(-6)
M) was found to double water and urea efflux but increased Ringer perfusion
rate by only 33%. Drastic changes in perfusion rate (by clamping) produced
smaller changes of both efflux rates. Epinephrine-stimulated increase in
water and urea efflux, and perfusion rate, was blocked by propranolol
(beta-blocker) but not by phentolamine (alpha-blocker). Both blockers
together canceled out all epinephrine effects. Epinephrine increased water
influx across isolated unperfused gill arches, the effect again being
blocked by propranolol but not by phentolamine. Both blockers together
canceled any epinephrine effect. We conclude that epinephrine alters
branchial vascular flow and functional surface area via alpha- and
beta-adrenergic receptors, but also increases branchial permeability to
water and probably urea, via beta-adrenergic receptors. To test the
validity of the perfused head technique, water and urea efflux rates were
compared with in vivo values.
