Abstract 96

Introduction: We have previously shown that antenatal treatment with betamethasone before preterm delivery reduces lung hyaluronan (HA) in rabbit pups born at gestational ages (GA) of 25 and 27 days, but had no effect at a GA of 28 days. We hypothesize that terbutaline, aβ2-adrenergic agonist, known to decrease airway epithelial water transport, might influence lung HA concentration and water immobilization.

Methods: Rabbit dams with timed pregnancies were injected one day before delivery with 30 µg terbutaline or saline (controls). Pups were delivered at 27, 28 and 29 days of gestation by cesarian section, and killed immediately. The trachea was tied and lungs removed en bloc. Wet/dry lung weight ratios (W/D) were determined using freeze-drying, and HA concentrations (conc.) were determined with Pharmacia's HA kit.

Results: At a GA of 27 days control pups (n=23) had a mean(± SEM) HA conc. of 494.2 ± 25.4 µg/g dry lung weight, and a W/D of 9.1 ± 0.1. Pups of dams antenatally treated with terbutaline (n=28) had a lung HA conc. and a W/D ratio not different from controls. At a GA of 28 and 29 days control pups (n=27, n=28) had mean HA conc. of 326.3 ± 18.2 and 265.2 ± 12.7 µg/g dry lung weight, respectively, and W/D ratios of 9.8 ± 0.1 and 9.4 ± 0.1, respectively. Pups of dams antenatally treated with terbutaline (p=23, n=25) showed significantly lower (p=0.034, p<0.001) HA conc. of 255.2± 16.5 and 171.3 ± 15.1 µg/g dry lung weight, respectively, than controls, and W/D ratios not different from controls.

Conclusion: Preterm rabbit pups born at a GA of 28 and 29 days of dams given antenatal terbutaline have lower lung HA than control pups.