Abstract
Unsaturated long chain fatty acids modulate hormone secretion from a variety of endocrine
glands, including the adrenal cortex. Oleic acid and linoleic acid have been shown
to stimulate production of glucocorticoids in the absence of adrenocorticotropic hormone,
but at a high concentration appeared to inhibit the action of this hormone. In the
present study, the concentration dependence of the inhibitory actions of these two
fatty acids was tested in collagenase-dispersed rat adrenal fasciculata cells, and
the effects of both lipids on cAMP production were also determined. Adrenocorticotropic
hormone stimulated steroid production from isolated cells approximately ten-fold above
unstimulated cells. Oleic and linoleic acid significantly inhibited the response to
this hormone by 44% and 54%, respectively. The half-maximally effective inhibitory
concentration of both lipids was between 75-100 µM. A maximal concentration of adrenocorticotropic
hormone increased cAMP secretion 138-fold above unstimulated cells. Oleic and linoleic
acids inhibited the increase in cAMP secretion by 47% and 33%, respectively. It is
concluded that pathophysiological concentrations of unsaturated fatty acids inhibit
the action of adrenocorticotropic hormone on the adrenal gland, and that the mechanism
of action of the lipids may be partly via inhibition of cAMP production.
Key words
Oleic Acid - Linoleic Acid - Corticosterone - Rat
