Abstract
C and E, the major lung structural proteins, increase as a fraction of dry lung weight throughout development. Since connective tissue metabolism is known to be effected by corticosteroids, we sought to determine the effect of antenatal exposure to betamethasone (B) on the C and E content of the lungs of prematurely delivered fetal rabbits. Pregnant does were injected with either saline (control) or B (0.2 mg/kg) at 48 and 24 hours prior to sacrifice which was at 24, 27, or 29 days gestation (term = 31). Fetuses were delivered by hysterotomy and weighed, after which their lungs were removed and lyophilized. E was isolated from aliquots of dried lungs by hot alkali digestion. Total lung hydroxyproline (OH-PRO) and E OH-PRO were determined by a colorometric assay and expressed as ug OH-PRO/100 mg dry lung. The difference between these two values was taken as a measure of lung C. C (ug OH-PRO/100 tag dry lung) in control fetuses increased from a mean of 262 at 24 days to 375 at 29 days (p<.01). Over the same period, E (ug OH-PRO/100 mg dry lung) increased from a mean of 4 to 11 (p<.01). Note that a steroid effect was demonstrated at 24, 27, and 29 days by a decrease in body weight (vs. controls) of 25%, 34%, and 33% respectively. At 24 days B increased C by 25% and E by 100%; at 27 days B increased C by 20% but had little effect on E; at 29 days B had little effect on C or E. These preliminary results suggest that steroid effects on lung connective tissue are significant but only at certain gestational ages.
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Jacobs, H., Lima, D., Mercuric, M. et al. STEROID EFFECTS ON LUNG COLLAGEN (C) AND ELASTIN (E) ARE DEPENDENT ON GESTATIONAL AGE. Pediatr Res 21 (Suppl 4), 216 (1987). https://doi.org/10.1203/00006450-198704010-00298
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DOI: https://doi.org/10.1203/00006450-198704010-00298