AJP - Heart and Circulatory Physiology, Vol 253, Issue 1 66-H74, Copyright © 1987 by American Physiological Society
Free and conjugated catecholamines in dog pulmonary artery: presence and pharmacological action
D. K. Rorie and G. M. Tyce
Free and conjugated forms of norepinephrine (NE) and dopamine (DA) were
detected in dog pulmonary artery, and small amounts were released during
2-Hz electrical stimulation. Hydrolysis of the conjugates by acid boiling
and by enzymes indicated that they were primarily sulfates, but traces of
glucuronide may also have been present. After isolation by column
chromatography, free and conjugated amines were quantitated using liquid
chromatography with electrochemical detection. Pulmonary artery tissue
contained (in ng) 1,240 +/- 100 free NE, 15 +/- 5 conjugated NE, 47 +/- 6
free DA, and 2 +/- 0.3 conjugated DA/g tissue (means +/- SE). When strips
of pulmonary artery were immersed in [3H]NE small amounts of [3H]NE sulfate
were synthesized. The release of conjugated NE was not calcium dependent
but release was attenuated somewhat by tetrodotoxin. Removal of endothelium
did not change tissue content of conjugated or of free NE nor the amounts
measured in superfusate. Small amounts of free DA were also detected in
tissues and in superfusate during stimulation, but only when calcium was
present in the superfusion fluid. Norepinephrine sulfate was not a potent
agonist at either pre- or postsynaptic alpha-receptors; the agonist
activity seen with high concentrations of norepinephrine sulfate seems
likely to have been due at least in part to trace contamination by free NE.
