Saturated fatty acids suppress adrenocorticotropic hormone (ACTH) release from rat anterior pituitary cells in vitro

We studied whether fatty acids modify adrenocorticotropic hormone (ACTH) release induced by stimulation with corticotropin-releasing hormone (CRH) from rat anterior pituitary cells. Stimulation with CRH (0.01-100 nmol/l) significantly and concentration-dependently increased ACTH release, which was synergistically enhanced by the simultaneous stimulation with 1 nmol/l arginine-vasopressin. Addition of saturated fatty acids (butyrate, caprylate, laurate, palmitate and stearate) in a medium at 1 mmol/l, despite effects on the basal release, significantly reduced the ACTH release induced by CRH (1 nmol/l) stimulation. Caprylate suppressed ACTH release in a concentration- dependent manner. However, unsaturated C18 and C20 fatty acids (oleate, linolate, linolenate and arachidonate) at 1 mmol/l significantly increased the basal release, but none of them suppressed CRH (1 nmol/l)-induced ACTH release. In the presence of caprylate (1 mmol/l), CRH (1 nmol/l)-stimulated increase in cellular calcium ion concentration was diminished. From these results we conclude that saturated fatty acids have a suppressing effect on CRH-induced ACTH increase in primary cultured rat anterior pituitary cells.