Growth hormone administration to long-living dwarf mice alters multiple components of the antioxidative defense system.

Endocrine hormones are thought to be involved in processes that contribute to aging. Long-living dwarf mice are growth hormone (GH)-deficient and exhibit enhanced expression of antioxidative defense molecules when compared to normal, wild type littermates. In this study, 3- and 12-month-old Ames dwarf mice received with 50 microg GH or saline for 7 days. Tissues were collected and assayed for several antioxidant molecules. In addition to increased body and liver weights, GH treatment of dwarf mice decreased liver, kidney and heart catalase protein (P < 0.05). Catalase activity was significantly decreased in kidney and heart tissues of mice receiving GH compared to dwarf mice treated with saline. Glutathione peroxidase (GPX) protein was significantly reduced in liver, kidney and muscle of GH-treated mice (P < or = 0.03). Likewise, the activity of GPX was decreased in liver and kidney tissues following GH administration (P< or = 0.04). Exogenous GH increased glutathione levels in brain, muscle and liver (P< or = 0.03) compared to saline controls. This evidence, along with previous data, suggests that GH suppresses key components of systems that counter oxidative stress. Reductions in GH and IGF-1 signaling contribute to extended life spans in a variety of species, which may be partially explained by an increased ability to neutralize deleterious byproducts of metabolism.