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A 4% paraformaldehyde‐fixed GH3 cells were incubated with goat anti‐GH antibodies (1:200, sc‐10365, Santa Cruz) and then with FITC‐conjugated IgG (1:1000, Thermo Fisher). For Pit‐1 staining, cells were incubated with rabbit anti‐Pit‐1 antibodies (1:200, sc‐442, Santa Cruz) followed by TRITC‐conjugated IgG (1:1000, Invitrogen). The nuclei were stained with DAPI (1:1000, Invitrogen). After treatment, the cells were immediately observed under a fluorescence microscope.

For total protein extraction and Western blot, we carried out in accordance with a method previously described.²⁰ The blots were probed with the following primary antibodies: BiP (1:1000, Proteintech, 11587‐1‐ap), p‐IRE1α (1:1000, Abcam, ab124945), IRE1α (1:1000, Abcam, ab37073), p‐eIF2α (1:1000, CST, 3597), eIF2α (1:1000, CST, 9722), ATF6 (1:1000, Abcam, ab122897), XBP1 (1:1000, sc‐7160, Santa Cruz), Pit‐1 (1:1000, sc‐442, Santa Cruz), GH (1:1000, sc‐10365, Santa Cruz), and GAPDH (1:7500, 60004‐I‐Ig, Proteintech). The blots were incubated with corresponding secondary antibodies conjugated to horseradish peroxidase (HRP) (ZSGB‐ Bio) at a dilution of 1:5000.