Static lung compliance during the development of the bullfrog, Rana catesbeiana

The static compliance of excised lungs was measured during the metamorphic development of the bullfrog, Rana catesbeiana. Absolute static compliance of excised lungs increased with developmental stage from 0.02(+/- 0.01 SD) ml/cm H2O at Taylor-Kollros (TK) stage III to 34.67(+/- 15.00 SD) ml/cm H2O for adults. When static lung compliance was standardized by dividing by the lung volume at 4 cm H2O transmural pressure (approximately maximal capacity), lung compliance was relatively constant during early development and increased at the onset of metamorphic climax (TK stage XX). Although the absolute lung compliances of developing tadpoles are small, the volume-specific compliances are three to four times greater than those of some mammals. The compliance-independent index of hysteresis also increased during development from 0.0008(+/- 0.0006 SD) cm at TK stage V to 1.36(+/- 1.21 SD) cm for adults suggesting increases in pulmonary structural complexity and/or an increase in the production and secretion of a pulmonary surfactant-like substance. These developmental changes in pulmonary compliance and hysteresis mirror the increasing utility of the lung for gas exchange during the metamorphosis of the bullfrog.