Uptake, distribution, and turnover of catecholamine radiolabel in the goldfish, Carassius auratus L.

Abstract

As the uptake, distribution, and turnover of epinephrine and norepinephrine are largely unknown in teleosts, the relative tissue affinities for these circulating catecholamines were evaluated in the goldfish, Carassius auratus L. Since sufficient circulating levels of catecholamines available for uptake by tissues in vivo are a transient event occurring after stress, it was decided to investigate the uptake and decline of radiolabeled catecholamines over a short period of time, noting that uptake would coincide with high endogenous levels from handling stress while decline would be unaffected by stress. Fish injected with l-[3H]norepinephrine and dl-[carbinol-14C]epinephrine were killed from 0.5 to 1024 min postinjection, and the catecholamine radiolabels determined in 19 tissues. Six different uptake and retention patterns for individual tissues were present, but all tissues examined showed preference for the norepinephrine radiolabel. Among the excretory mechanisms in the goldfish, the liver is prominent in catecholamine elimination via the bile. A blood–brain barrier appears present for epinephrine, but not for norepinephrine; epinephrine is excluded from the hypothalamus and pituitary. Further, adipose tissue takes up only norepinephrine. In some teleostean tissues, therefore, the two catecholamines are handled differently than in the comparable mammalian tissues.