Postpneumonectomy lung growth following thyroparathyroidectomy

Hormonal regulation of compensatory lung growth is not well understood, but it may be similar to that during compensatory growth of other organs. Liver regeneration is blocked by hypocalcemia in thyroparathyroidectomized (TPX) animals. Although calcium status is an important regulator of growth in many biological systems, the effect of TPX on compensatory lung growth is unknown. In male Sprague-Dawley rats, TPX lowered blood ionized calcium by 42% (p < .01) within two days; it remained depressed for at least one additional week. Thyroid-intact and TPX animals were therefore subjected either to sham thoracotomy or to left pneumonectomy on post-TPX day 2. Growth of the right lung was assessed on day 9 when, in pneumonectomized animals, lung mass had increased 23% (p < .01). TPX had no effect on right lung mass in sham animals. Similarly, TPX had no effect on the postpneumonectomy increase in right lung mass, which reached 118% (p < .01) of that in TPX controls. Analysis of right lung DNA, RNA, and protein concentrations on day 9 revealed that tissue macromolecule content increased postoperatively in both PNX and TPX/PNX rats in proportion to lung growth. These results demonstrate that postpneumonectomy compensatory growth of the lung is not blocked in the thyroparathyroprivic hypocalcemic rat.