The pituitary gland is required for protection against lethal effects of Salmonella typhimurium

One-half of pituitary-intact or sham-operated rats survive infection with 10⁹ colony-forming units of Salmonella typhimurium, whereas rats without a pituitary gland all die within a few days. When the dose of S. typhimurium is reduced 600-fold, 15-25% of the hypophysectomized rats survive, and the survival rate is significantly enhanced by administration of tetracycline, recombinant Interferon γ (IFN-γ), or recombinant growth hormone (GH). The protective effect of GH is abolished by heat inactivation or with an antibody to GH. Spleens from normal and hypophysectomized rats treated with tetracycline, IFN-γ, or GH have 59-99% fewer bacteria 5 days after infection as compared to control rats. Peritoneal macrophages from hypophysectomized rats that are infected in vitro with S. typhimurium kill half as many extracellular bacteria as compared to pituitary-intact rats, and this bactericidal capacity is significantly augmented 75-95% by either GH or IFN-γ. These data establish that the pituitary gland is essential for homeostasis during an infectious episode and that GH plays an important role in host resistance by augmenting the ability of macrophages to kill S. typhimurium. (.