EFFECT OF CORTICOSTEROIDS ON THE DOSE RESPONSE OF SURFACTANT IN PRETERM RABBITS

摘要

We injected 16 pregnant does with .1 mg/kg·day betamethasone (B) or vehicle (C) on the 2 days before C-section at day 27. The newborns were tracheostomized and randomly treated with normal saline (Sal), 5, 15, 30, or 50 mg/kg of rabbit surfactant (SA). They were then ventilated for 10 min with a ventilator-plethysmograph at tidal volumes of 12-15 ml/kg. After lung collapse, air pressure-volume inflation (Vi) and deflation (Vd) curves were measured from 0 (V0) to 35 cm H2O (V35) with volumes expressed as mean±SEM for ml/g dry lung wt and lung stability index (LSI) as (2V5±V10-3V0)/(2V35-2V0).There were significant differences for Vi35, Vd35, Vd15 and compliance between C and B at each dose (p<.01). The similarity of values for LSI between C and B showed that the steroid effect was not related to changing surface tension. Steroids have a threshold and synergistic effect on surfactant at low doses.