AJP - Endocrinology and Metabolism, Vol 265, Issue 2 E184-E189, Copyright © 1993 by American Physiological Society
Free and conjugated catecholamines and serotonin in canine thoracic duct lymph: effects of feeding
Y. K. Chen, H. M. Richter 3rd, V. L. Go and G. M. Tyce
Department of Gastroenterology, Mayo Clinic, Rochester, Minnesota 55905.
The source and fate of sulfoconjugated catecholamines present in plasma are
not known. Sulfated norepinephrine has been shown to overflow together with
free norepinephrine from a typical peripheral neuroeffector junction. Some
released free norepinephrine is removed via the lymphatic system, but it is
not known whether sulfated catecholamines are removed similarly. Serotonin,
another biogenic amine, is released from the enterochromaffin cells into
portal blood. The aims of the present study were to determine whether
conjugated catecholamines and serotonin could be detected in thoracic duct
lymph of dogs and to compare concentrations in lymph with those in samples
of portal blood collected before and after the dogs were fed. A method is
described for the extraction and purification of free and conjugated
catecholamines and serotonin from lymph. In lymph and in plasma, there were
similar concentrations of free (0.2-0.4 ng/ml) and conjugated (0.1-0.2
ng/ml) norepinephrine and of conjugated dopamine (0.2-1.0 ng/ml). The
concentrations of free serotonin were much lower in lymph (0.1-0.2 ng/ml)
than in portal blood (100-200 ng/ml). Small amounts of conjugated serotonin
(0.1-0.4 ng/ml) were detected in lymph but were not detected in plasma.
Feeding caused increases in concentration of conjugated dopamine in lymph
and in plasma and small increases in the output of free norepinephrine and
free and conjugated serotonin in lymph.
