AJP - Regulatory, Integrative and Comparative Physiology, Vol 250, Issue 3 519-R525, Copyright © 1986 by American Physiological Society
Plasma clearance, metabolism, and tissue accumulation of 3H-labeled catecholamines in trout
N. P. Nekvasil and K. R. Olson
Plasma clearance, metabolism, and tissue accumulation of [3H]norepinephrine
(NE) and [3H]epinephrine (E) were measured after injection into the dorsal
aorta of chronically catheterized trout, Salmo gairdneri. Sucrose, an inert
volume marker, was injected with the catecholamines (CAs). Ion-exchange
chromatography was used to separate unmetabolized CAs from deaminated and
O-methylated metabolites in plasma. Both CAs are cleared from plasma at an
exponential two-component rate. By 10 min postinjection, CA-specific
extraction lowered plasma [3H]NE by 65% and [3H]E by 50%. Over 80% of the
3H remaining in plasma 10 min after injection was metabolized to
O-methylated and deaminated products. Thus trout are able to quickly and
efficiently lower circulating CA levels through tissue accumulation and
metabolism. Kidney, liver, spleen, and atrium accumulate more CA than other
tissues, although most tissues bind CA to some extent. Gills preferentially
accumulate CAs over sucrose. Skeletal muscle has a low affinity for CAs but
by virtue of its large mass may be an important organ in CA metabolism. NE
is removed from the circulation faster, and more NE is bound to tissues
than E. A blood-brain barrier for E but not NE was observed.
