INTERFERON-GAMMA INHIBITS STIMULATED ADRENOCORTICOTROPIN, PROLACTIN, AND GROWTH-HORMONE SECRETION IN NORMAL RAT ANTERIOR-PITUITARY CELL-CULTURES

Preincubation of rat anterior pituitary (AP) cells with homologous interferon-γ (IFN-γ) caused a dose-dependent inhibition of ACTH secretion stimulated byCRF. The effect was seen in both monolayer and aggregate AP cell cultures and was not due to cytotoxicity. In monolayer cultures IFN-γ also inhibited PRL and GH release stimulated by various hypothalamic releasing factors. IFN-γ did not affect the time kinetics of the ACTH response to CRF. The dose needed for half-maximal inhibition amounted to approximately 1 (antiviral) U/ml. The effect of IFN-γ was abrogated by an IFN-γ neutralizing monoclonal antibody. Furthermore, ACTH secretion by the AP cells was not affected by the anti-IFN-γ antibody added alone, indicating that in the culture system no endogenous IFN-γ is operational in regulating the ACTH response studied. Of the other cytokines tested [interleukin-1 (IL-1), tumor necrosis factor-α (TNF-α), interleukin-6(IL-6), and interferon-α/β (IFN-α/β)] only TNF-α and IL-6 were found toinhibit CRF-stimulated ACTH release, although this inhibition was less pronounced than that caused by IFN-γ. Lipopolysaccharide, even at high doses, did not significantly inhibit the ACTH response to CRFThese results identify IFN-γ as one of the inflammatory cytokines that, like IL-1, TNF-α, and IL-6, have the potential to regulate pituitary function. © 1990 by The Endocrine Society.