AJP - Renal Physiology, Vol 258, Issue 2 287-F291, Copyright © 1990 by American Physiological Society
Origin of dopamine in the rat adrenal cortex
N. T. Buu and C. Lussier
Laboratory of the Autonomic Nervous System, Clinical Research Institute of Montreal, Quebec, Canada.
The hypothesis that dopamine (DA) is involved in the control of aldosterone
secretion is given some support by the finding of DA in the adrenal cortex
of several species, but the source of this DA is not known. This study
showed that the administration of L-dopa to intact rats or medullectomized
rats caused a significant DA increase in the adrenal cortex. The DA
increase in the cortex was more pronounced than in the medulla, coincident
with higher L-dopa uptake by the cortical tissue. Tyrosine administration
raised DA levels only in the medulla. Sympathectomy of the rat by
6-hydroxydopamine treatment did not affect DA basal levels in the cortex or
the DA increase in this tissue after L-dopa injection.
3,4-Dihydroxyphenylacetic acid (DOPAC) is detectable in the adrenal cortex
but not in the adrenal medulla, and DOPAC levels increased significantly
after L-dopa, which indicates monoamine oxidase (MAO) activity within the
adrenal cortex. Because 6-hydroxydopamine pretreatment did not alter DOPAC
levels, cortical MAO may be located outside catecholaminergic neurons. The
results established circulating L-dopa as a precursor for DA in the adrenal
cortex of the rat. They also showed that tyrosine hydroxylase activity is
absent from the adrenal cortex of this species.
