Evidence that folliculo-stellate cells mediate the inhibitory effect of Japanese Kampo medicine, Unkei-to, on growth hormone secretion in rat anterior pituitary cell cultures

PROBLEM: Cytokine-induced neutrophil chemoattractant (CINC) was reported to influence anterior pituitary hormone release. We recently found that Unkei-to, one of the Japanese Kampo medicines, stimulated CINC secretion by rat anterior pituitary cells and the pituitary folliculo-stellate (FS)-like cell line (TtT/GF). Therefore, the effect of Unkei-to on growth hormone (GH) secretion by rat anterior pituitary cells was investigated. METHOD OF STUDY: Dispersed normal anterior pituitary cells, the folliculo-stellate-like cell line TtT/GF, and the GH(3) cell were used to test the effect of Unkei-to on GH secretion. In reconstitutive coculture experiments, TtT/GF cells were mixed with GH(3) cells at a ratio (TtT/GF cells: GH(3) cells) of 1:99. From this mixture, cells were seeded onto plates at a density of 10(4) cells/well and were cultured for 5 days. The cells were then used in the experiments. RESULTS: Unkei-to at 20 mu g/ml significantly inhibited GH secretion by normal anterior ptuitary cells within 12 hr of incubation. In contrast Unkei-to stimulated GH secretion by GH(3) cells in a time-and dose-dependent manner, suggesting that an accessory cell type was involved. To assess the contribution of CINC as a paracrine factor, an experiment using a reconstitutive coculture system was performed, and Unkei-to was found to inhibit GH secretion when GH3 cells were cocultured with TtT/GF cells. The addition of anti-CINC antibody to the reconstitutive coculture system antagonized Unkei-to-inhibited GH secretion. CONCLUSION: CINC, which was secreted from FS cells by Unkei-to, may be responsible for mediating the inhibitory effect of Unkei-to on GH secretion by rat anterior pituitary cells.