MORPHOLOGICAL PECULIARITIES OF RESPIRATORY COMPARTMENTS OF ARCTIC ANIMAL LUNGS

Background: Morphological and ultrastructural peculiarities of interal veolar septa in endemic arctic animals (reindeer, polar fox, lemming) are compared with laboratory animals (rat,dog). Methods: For light mic roscopy, tissue samples were taken from the central and peripheral sec tions of all lobes of the right lung, They were fixed in 10% neutral f ormalin and embedded in paraffin, For electron microscopy, samples wer e taken from subpleural sections of the caudal lobe of the right lung, fixed in 4% paraformaldehyde for 24 hours, subsequently postfixed in 2% OsO4 . for 2.0 hours, Samples were dehydrated in acetone and embedd ed in a mixture of Epon 812 and Araldite, Ultrathin sections were phot ographed at a magnification of x 4,000, For each interalveolar septum, lengths and diameters were recorded and the squares of septa surface, air-blood barrier surface and the number of the structures were deter mined, The topography of capillaries and the ultrastructure of interst itium were described. Results: Acini in the arctic animals (reindeer, polar fox, lemming) are compact, In all lobes they are fully expanded and uniformly filled with air, There is no physiological atelectasis, Alveoli appear straight and homogeneous in form and size, In the polar fox, the quantity of interalveolar pores of Kohn is twice that in the dog, The number of pores in the lemming are similar to those in the r at but their size is 1.6 times greater in diameter, In arctic animals more capillaries connect with both alveolar surfaces by an air-blood b arrier and simultaneously participate in the gas exchange of two adjoi ning alveoli, In the polar fox and lemming the thickness of the air-bl ood barrier is 1.3-1.4 times less than that in the dog and rat. Conclu sions: The set of morpho-functional peculiarities of the acini of arct ic animals allows for an increase in gas exchange in the respiratory c ompartments of the lungs and provides necessary oxygenation of arteria l blood at a low partial pressure of oxygen in the alveolar gas. (C) 1 997 Wiley-Liss, Inc.