Morphometric changes in the lungs of rats following adrenalectomy supplemented by desiccated thyroid.

Abstract

AbstractStudies were conducted to assess the effects of thyrotoxicosis on the lung of the adult adrenalectomized rat. The animals were divided into four groups of seven animals each: Adrenalectomized animals receiving desiccated thyroid in their food for 8 weeks, adrenalectomized animals, and sham‐operated animals receiving regular laboratory chow. Unoperated animals were used as controls. There were no differences in the pressure‐volume curves or morphometric parameters between unoperated‐control and sham‐operated animals; therefore they will be collectively reported as control animals. Lung volume in the thyroid‐treated animals showed an increase of 19% in pressure‐volume studies when compared with the other groups. Lung volume determined morphometrically demonstrated a 19% increase in volume when adrenalectomized thyroid‐treated rats were compared with control amimals, and a 29% increase compared with adrenalectomized animals. The thyroid‐treated animals also showed an alveolar surface density (Sva) increase of 58% over control and 28% over adrenalectomized animals. In addition, alveolar surface area (Sa) of the treated animals was 89% greater than control and 65% greater than adrenalectomized animals. The marked difference in the surface‐to‐volume ratio indicates that alveoli were smaller and more numerous in the lungs from the thyroid‐treated animals. These results are readily apparent in examination of light microscopic sections of the lung specimens from the four groups of animals. These findings indicate that chronic thyroid administration results in a significant increase in lung volume, which we attribute to increased alveolar partitioning.