The lung of shrews: morphometric estimation of diffusion capacity.

The lungs of 16 shrews from 8 species (Sorex minutus, Neomys fodiens, Suncus etruscus, Crocidura russula, C. juvenetae, C. poensis, C. flavescens, C. giffardi) ranging in body weight from 2.2 to 100 g were studied by morphometry in order to compare the structural diffusion capacity for oxygen. DL02, with the oxygen consumption, VO2, measured on the same animals. VO2 was determined by short term measurements using a respirometer. DLO2 was estimated morphometrically. Both parameters demonstrated good coincidence in their allometric behaviour, establishing further progress in structure-function relationship in the respiratory apparatus. Whereas VO2 as well as DLO2 of shrews with a body weight W greater than 5 g follow the same allometric function established for mammals in general, the values for shrews with W less than 5 g exhibit significantly higher values. It appears that the pulmonary gas exchange parenchyma of these smallest mammals is well suited to supply the organism with the comparatively high levels of O2 required by the high metabolic rates, exhibiting a structural adaptation of the lung to higher VO2.