Influence of thyroxine on adult rat lung oxygen consumption and ultrastructure

We studied the oxygen consumption (QO2) of lung slices and the ultrastructure of the pulmonary granular pneumocyte in rats whose level of circulating thyroxine was altered. Rats given thyroxine for 6 days (1.0 mg-kg-1-day-1) and sacrificed on the 7th day had a serum thyroxine level of 18.9 +/- 2.7 mug/100 ml (mean +/- SD); rats given diluent alone for 6 days had a serum thyroxine level of 4.67 +/- 0.53 mug/100 ml. Rats subjected to a sham thyroidectomy has a serum thyroxine level of 7.27 +/- 1.47 mug/100 ml, whereas rats subjected to thyroidectomy had a serum thyroxine level of 1.13 +/- 0.55 mug/100 ml when sacrificed. The QO2 of lung slices from rats with high levels of circulating thyroxine was significantly greater than that of rats that received diluent alone. The QO2 of slices from rats whose thyroid glands were excised was significantly lower than the QO2 of slices from sham-operated rats. We did not find quantitative ultrastructural differences in granular pneumocyte mitochondria and lamellar bodies of rats given thyroxine compared to rats given diluent or between rats subjected to sham thyroidectomy compared to rats whose thyroid glands were removed.