Ultrastructure of canine type II pneumocytes during hypothermic ischemia of the lung: A study by means of conventional and energy filtering transmission electron microscopy and stereology

Alterations in pulmonary surfactant have been reported to be associated wit h ischemia/reperfusion injury in experimental and clinical lung transplanta tion. It is unknown whether these alterations are due to damage to surfacta nt synthesizing type II pneumocytes during hypothermic ischemic storage. Th e aim of the present study was to examine the effects of hypothermic ischem ic storage of the lung on canine type II pneumocytes by means of convention al (CTEM) and energy filtering TEM (EFTEM) and stereology. The lungs of 18 dogs were fixed for TEM immediately after cardiac arrest (6 double lungs) a nd after storage in Tutofusin(R) at 4 degreesC for 20 min, 4 hr, 8 hr, and 12 hr (6 single lungs, respectively). Using a systematic uniform random sam pling scheme, type II pneumocytes were analyzed qualitatively and stereolog ically. The relative phosphorus content of cell organelles, especially the surfactant, containing lamellar bodies, was investigated by EFTEM. By CTEM, no major qualitative alterations could be observed in type II pneumocytes of the experimental groups. Stereologically, no significant changes in the volume densities or the volume-to-surface ratios of type II pneumocytes and their lamellar bodies were found. By EFTEM, the highest intracellular phos phorus signals were recorded over lamellar bodies in all experimental group s. No changes in the phosphorus signals were observed during ischemia. Thes e results indicate that the ultrastructure of canine type II pneumocytes an d their lamellar bodies is not affected by hypothermic ischemia of the lung up to 12 hr. Structural preservation of intracellular surfactant is possib le during prolonged ischemic lung storage. Anat Rec 263:118-126, 2001. (C) 2001 Wiley-Liss, Inc.