To evaluate the concept that lung elastin degradation is accelerated in homozygous alpha-1-antitrypsin (AAT) deficient persons, we prepared acid hydrolysates of urine and used a radioimmunoassay for desmosine to measure urine concentrations of this elastin-specific cross-link in such persons and in control subjects. Excretion of desmosine in 17 homozygous AAT-deficient (PiZZ) patients with emphysema was compared with that in 27 patients with interstitial lung diseases (16 sarcoid, 5 idiopathic pulmonary fibrosis, 6 other interstitial lung diseases) and 26 healthy subjects. Both smokers and nonsmokers were present in all groups. Urinary desmosine concentration (microgram/100 mg creatinine) was 2.35 +/- 0.93 in the PiZZ patients, 2.49 +/- 1.01 in those with interstitial lung disease, and 2.05 +/- 0.54 in the healthy control subjects (p greater than 0.1, all comparisons). Because abnormal pulmonary elastolysis may be largely completed before symptoms of emphysema develop in AAT-deficient persons, we also tested 6 asymptomatic adults with homozygous AAT deficiency (PiZZ) and 5 PiZZ children. Urine desmosine (microgram/100 mg creatinine) was not significantly elevated in either group compared with that in the age-matched control subjects, although children (PiZZ and age-matched controls) showed higher excretions than did adults (6 asymptomatic PiZZ adults, 2.60 +/- 0.91; 5 PiZZ children, 3.27 +/- 0.62; 10 control children, 3.61 +/- 0.62). These data suggest that pathologic lung elastolysis in the PiZZ subject may constitute too small a fraction of total-body elastin turnover to be detected by this method.(ABSTRACT TRUNCATED AT 250 WORDS)