Thyroid hormone influences glucocorticoid receptor levels in the neonatal rat lung.

In the early postnatal rat, the level of glucocorticoid receptors in the lung increases during the first week of life (5) when thyroid hormone ontogenesis occurs (6). Inhibition of thyroid function in neonatal rat pups by combined pre- and postnatal propylthiouracil treatment abolished the developmental rise in pulmonary glucocorticoid receptor levels. A single injection of 1 microgram T3 to these pups caused an elevation in receptor concentration to euthyroid values in 48 h. These findings support the hypothesis that thyroid hormone promotes tissue receptivity to glucocorticoids in the developing lung of the infant rat.