Desmosine Radioimmunoassay for Measuring Elastin DegradationIn Vivo1–3

Abstract

Desmosine is a cross-link amino acid unique to elastin. During turnover in the body, desmosine is not reused. Desmosine is not absorbed from the intestine. All desmosine released during elastin metabolism is excreted in the urine attached to low MW peptides. Measurement of desmosine in acid-hydrolysates of urine might be used to monitor elastin breakdown in several pathologic states, including pulmonary emphysema. A sensitive, highly specific radioimmunoassay capable of detecting as little as 200 pg of desmosine in acid-hydrolysates of urine is described. The assay was specific for desmosine; cross-reactivity with merodesmosine, isodesmosine, lysine and mixed amino acids was 0.25%, 0.1%, < 0.0003% and 0%, respectively. Normal, nonsmoking patients (23) had a mean 24 h desmosine excretion of 47 .+-. 15 .mu.g. In a group of smokers with evidence of chronic obstructive lung disease and/or lung infection, the values for desmosine excretion ranged from 40-400 .mu.g/24 h. Desmosine radioimmunoassay may find application in the study of diseases involving increased destruction of elastin in the body.