Abstract 251 Poster Session III, Monday, 5/3 (poster 98)

Hypoxia is associated with growth impairment in many diseases of infants and children but the mechanisms are not fully understood. We reasoned that the growth recovery from a relatively brief exposure to moderate hypoxia would be rapid since tissue oxygenation is restored virtually instantaneously. Six, 21 d. o. female, Sprague-Dawley rats were exposed to an FiO2 of 0.12 in a metabolic chamber for 7 days, and 14 animals were used as controls (breathing room air). Body weight was measured daily and growth rate was calculated (Figure -mean± SD). Serum levels of insulin-like growth factor-I (IGF-I, by RIA), tumor necrosis factor-α (TNF-α, by ELISA), and interleukin-6 (IL-6, by ELISA) were measured 7 days after the exposure to hypoxia. Surprisingly, after an initial marked suppression, growth rate returned to normal after only one day even as hypoxia continued. Moreover, the post-hypoxia rebound in growth rate was not nearly as dramatic as the initial reduction upon exposure. The data suggest that factors other than oxygen availability itself (perhaps, the regulation of circulating growth factors) modulate growth rates in response to the hypoxic environment. Finally, by the seventh day of recovery, there was no evidence of depression of the growth factor IGF-I, or elevation of the cytokines TNF-α and IL-6, often observed acutely in response to hypoxic exposure.

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