Stereological estimation of the volume weighted mean volumes of alveoli and acinar pathways in the rat lung to characterise alterations after ischaemia/reperfusion

The aim of this study was to characterise pulmonary reimplantation injury i n isolated, perfused rat lungs following 2 h of cold ischaemia, and 50 min, of in vitro reperfusion. The effects of 2 differently composed lung preser vation solutions (low potassium Euro-Collins and Celsior; each n = 5) were examined in comparison with untreated, nonischaemic control lungs (n = 3). After fixation by vascular perfusion and tissue collection by systematic ra ndom sampling, the volume weighted mean volume ((V) over bar(v)) of alveoli and acinar pathways was estimated by light microscopic stereology using th e method of point sampled intercepts in plastic embedded, Azan-stained mate rial. Significantly higher (V) over bar(v) of alveoli and acinar paths was found in the Celsior group than in Euro-Collins preserved lungs. However, i n the controls the size of acinar pathways was similar to Celsior preserved lungs whereas alveolar size was comparable to preservation with Euro-Colli ns. The between-animal coefficient of variation of alveoli was very low in controls and Celsior preserved but higher in the Euro-Collins group. Size d istribution of alveoli and acinar paths in 15 size classes was largely homo geneous in all groups tested. In the Euro-Collins group the fractions of bo th class 1-alveoli and class 1-acinar paths significantly exceeded those of the other groups. Widely expanded alveoli (size classes 13-15) only occurr ed after preservation with Celsior whereas wider acinar paths (size class 1 5) were found in the Celsior group and in the controls. It is concluded tha t lung preservation with low-potassium Euro-Collins and Celsior solutions m ay act differently on distinct spaces in the distal gas-exchange regions of lungs. This may be due to selective effects on pulmonary surfactant activi ty and on elastic tissue elements in the alveolar ducts, respectively. Addi tionally, the method of point sampled intercepts is considered to be an eff icient tool to evaluate the effects of different preservation solutions on lung parenchyma.