DISTRIBUTION OF ELASTIN IN HAMSTERS AND THE TURNOVER RATES OF DIFFERENT ELASTIN POOLS

Desmosine (DES) and isodesmosine (IDES) concentration in the urine can be used as a noninvasive method of assessing degradation of mature el astin in normal and pathologic states, The present study was undertake n to determine the distribution of elastin among organs and tissues of normal hamsters, and to determine the turnover rates of two elastin-c ontaining organs (lung, thoracic aorta) as a reflection of their contr ibutions to DES and IDES excretion in the urine, Hamsters were metabol ically labeled at 5 days of age with C-14-lysine and studied at 1.5, 4 .5, 8, and 12 months of age. The aorta DES+IDES-associated radioactivi ty did not change significantly over the age span of 1.5-12 months, Lu ng DES+IDES-associated radioactivity decreased with a half-life of 420 days. Measurement of DES+IDES pools in other tissues, with relatively low concentrations of elastin, was carried out by the isotope dilutio n technique, At 12 months of age, the head and paws pool, skin, skelet al muscle, gastrointestinal tract, heart-liver-kidney-spleen pool, lun gs, and thoracic aorta represented 37%, 28%, 13%, 11%, 6%, 4%, and 1%, respectively, of total body DES+IDES. The organs with the highest DES +IDES-specific radioactivity at 12 months were heart-liver-kidney-sple en, lung, and gastrointestinal tract, with 310, 217, and 217 dpm/nmol, respectively, Skin had the lowest specific radioactivity, with 90 dpm /nmol. The specific radioactivity of DES+IDES in urine was 62 dpm/nmol at 12 months, down from 251 dpm/nmol at 1.5 months. These data clearl y indiciate that non-lung tissues contain a high proportion of the tot al body DES+IDES and suggest that pathology in these other pools of DE S+IDES could result in significant elevation of urinary DES+IDES. Neve rtheless, the relatively high specific radioactivity of DES+IDES in lu ng elastin as compared with urine makes monitoring labeled urinary DES +IDES in this animal model a sensitive tool for assessing elastin degr adation in experimental lung disease.