Elastin content of normal and emphysematous lung parenchyma

Abstract

Elastin destruction has been recognized as a crucial factor in the development of experimental pulmonary emphysema. However, no consistent alterations in lung elastin have as yet been demonstrated in human subjects with diffuse panacinar emphysema. In this study elastin content was measured in pulmonary parenchyma obtained by surgical biopsy and postmortem from eight patients with clinical, physiologic and morphologic criteria for panacinar emphysema, and postmortem from six normal adults. Concentrations of the elastin-specific amino acids, desmosine and isodesmosine, were determined both in the crude connective tissue of lung parenchyma and separately in elastin isolated by a modification of the Lansing method. Elastin proportions were then expressed as percent of lung parenchymal crude connective tissue. In lungs of six normal control subjects mean elastin was 30.5 percent standard deviation (SD) ± 3.69 (range 25.1 to 35.0 percent). In five patients the proportions of lung elastin were all below control: mean 12.1 percent SD ± 3.7 (range 9.0 to 17.5 percent). Three patients of this group had Pi phenotype MM; one had ZZ and one had MZ. In three additional patients (one with Pi MZ; two with Pi MM), all of whom had received glucocorticoid therapy (21 months to nine years), elastin proportions were similar to those observed in normal subjects: mean 36.8 percent SD ± 5.98 (range 31.7 to 43.4 percent). The amino acid composition of isolated elastin did not differ significantly between any of the groups. Results demonstrate reduced proportions of lung elastin in pulmonary emphysema except in patients treated with glucocorticoids which may decrease collagen synthesis and increase the relative proportions of elastin.