Desmosine is an
amino acid specific to
elastin. Animal studies suggest that urinary
desmosine (UD) represents endogenous
elastin degradation. Therefore, UD has previously been used to investigate endogenous elastolysis, but was not elevated in subjects with chronic obstructive airways disease (
COAD), although accelerated pulmonary elastolysis is thought to contribute to
COAD. We have investigated whether this reflects large day-to-day and between-subject variation in UD and whether, in man, dietary
desmosine contributes significantly to that in urine. Mean 24-hour UD output (over 5 consecutive days) from 10 asymptomatic subjects (5 males) was higher in males than females (77.4 +/- 9.6 and 40.2 +/- 5.0 nmol/24 hours, respectively; mean +/- SD, P less than .001), but not significantly different when expressed in terms of
creatinine (micrograms
desmosine/100 mg
creatinine: males, 2.5 +/- 0.4; females, 3.1 +/- 0.8; mean +/- SD). The lowest between-subject variation was observed when the mean of 5 days' 24-hour UD values was analyzed on the basis of gender (coefficient of variation [CV], 12.5%); when gender was not considered, the least between-subject variation was found for the mean of 5 days'
desmosine/
creatinine analysis (CV, 24.5%). Approximately 1% of dietary
desmosine (ingested as [3H]
elastin and [3H]
desmosine) was excreted in the urine within 24 hours, contributing approximately 15% of UD while on a normal diet. Although ingestion of a low
elastin diet (less than 1/10
desmosine/24 hours than a normal diet) resulted in lower within-subject variation in 24-hour UD excretion (mean CV decreased from 31.5% to 20.2%), the between-subject CV and UD levels did not alter.(ABSTRACT TRUNCATED AT 250 WORDS)