Compensatory lung growth: protein, DNA and RNA lung contents in undernourished trilobectomized rats1 Crescimento pulmonar compensatório: conteúdos pulmonares de proteína, DNA e RNA em ratos subnutridos trilobectomizados

Purpose: To demonstrate compensatory lung growth (CLG) by lung contents of proteins, DNA, and RNA in undernourished young adult rats, submitted to pulmonary trilobectomy. Methods: We used 137 male Wistar rats, randomly distributed into 9 groups; they were submitted to three treatments (control, thoracotomy, and trilobectomy), and sacrificed at three different times (7, 30, and 90 days). In trilobectomy we removed the right median, accessory, and caudal lobes. We studied lung proteins, DNA, and RNA contents. Results: In the cranial lobe and left lung, protein content was higher in trilobectomized rats however there was insufficient CLG to make up for the loss. The increase of DNA in the cranial lobe and left lung of trilobectomized rats was sufficient to compensate for this loss, resulting in a similar content to controls. RNA content in trilobectomized rats, was higher in the cranial lobe and left lung, more efficient in the cranial lobe, but less than in the other groups. Conclusions: CLG occurred in trilobectomized rats, probably with cell hyperplasia and little hypertrophy, due to the large DNA compensation and small RNA compensation. This was markedly different to wellnourished animals, who had pronounced hypertrophy.