Accumulating data indicate that interleukins can activate the hypothalamic-pituitary-adrenal (HPA) axis. We evaluated the effect of human recombinant interleukin-3 (IL-3) and interleukin-6 (IL-6) on cortisol secretion from adult human adrenocortical cells in primary culture. IL-3 and IL-6 (100 microg/L) equipotently stimulated basal cortisol secretion approximately 5-fold. The stimulatory effect was significant after 12 h (p<0.01) and maximum cortisol levels were induced after 48 h. In contrast to ACTH, which significantly induced cAMP levels in parallel to its steroidogenic effect, IL-3 or IL-6 had no significant effect on cAMP. Furthermore, we showed that specific inhibition of the cyclooxygenase pathway by indomethacin completely blocked the steroidogenic effect of IL-6 while the effect of IL-3 was not affected. In contrast, coincubation with nordihydroguaiaretic acid--a specific inhibitor of the lipoxygenase system--abolished IL-3 stimulated steroidogenesis but had no effect on IL-6 stimulated cortisol secretion. These findings indicate that IL-3 and IL-6 directly stimulate the steroidogenesis at the adrenal level through activation of different, cAMP-independent pathways. While the stimulatory effect of IL-6 on cortisol secretion from adult human adrenocortical cells seems to be mediated through the cyclooxygenase pathway, the effect of IL-3 on adrenocortical cortisol secretion is dependent on the lipoxygenase pathway.