Effect of hypoxia and high altitude on thyroidal iodine metabolism in the rat.

Abstract

In order to study the effects of hypoxia on thyroidal iodine metabolism, chambers were designed to maintain reduced concentrations of O2 at ambient barometric pressures. The resulting partial pressures of O2 simulated 15,000–18,000 feet altitude. Rats were kept in this environment for 7–9 days before they were injected with 131I- and killed. Thyroid weight was reduced only in the hypoxic animals previously fed a low iodine diet. Histology and radioautography suggested a “resting” gland in the hypoxic groups. The thyroidal accumulation of 131I- was decreased in the hypoxic animals in most experiments. The percentage of 131I- in the thyroidal homogenates was increased only in the iodine-deficient hypoxic groups. Chromatographic (collidine: H2O :NH3) analysis of pancreatin digests of these homogenates showed a marked decrease in T4-131I and T3-131I with a rise in D131IT. Studies carried out at 1, 3, 5, 7 and 37 days after groups of rats were transported to the summit of Pikes Peak, Colorado (14,100 ft) subst...