PRODUCTION OF INTERLEUKIN-6 BY ANTERIOR-PITUITARY CELLS-INVITRO

We recently reported that the cytokine interleukin-6 (IL-6) is a potent stimulator of anterior pituitary hormone release in vitro. Since IL-6 is not normally detectable in the blood, we hypothesized that IL-6 may be produced by the anterior pituitary in situ and thereby affect hormone secretion through paracrine or autocrine mechanisms. The present study demonstrates that cultured anterior pituitary cells sponta-neously secrete large quantities of IL-6 in vitro. IL-6 was detect-able in the incubation medium within 2 h, and by 8 h of culture had attained concentrations of 2000-4000 U/ml- 4 × 105 cells. IL-6 production was stimulated by phorbol myristate acetate (10-100 nM) approximately 2-fold and by lipopolysaccharide (0.001-10.0 μg/ml) 4-fold during 4-h incubations. In contrast, the cytokine recombinant human IL-1α had no effect on IL-6 release by cultured pituitary cells. Freshly dissected hemipitui- tary tissue also secreted more than 3000 U/ml IL-6 during a 4- h incubation. This secretion was enhanced 3-fold by 10 μg/ml lipopolysaccharide. Our results suggest that the anterior pitui-tary may produce IL-6 in situ, where it may function as an intrapituitary releasing factor. © 1990 by The Endocrine Society.