LUNG CuZn-SUPEROXIDE DISMUTASE GENE EXPRESSION AFTER INTRATRACHEAL INSTILLATION OF ANTIOXIDANT-SURFACTANT LIPOSOMES. † 2115

Abstract

Tolerance to oxidant injury requires the accumulation of increased amounts of antioxidant enzymes. Surfactant liposomes, encapsulating CuZn-superoxide dismutase (CuZn-SOD) and catalase, increase alveolar type II cell antioxidant activity and protect cells against oxidant stress (AJP 1993;265:L330). Intratracheal instillation of antioxidant-surfactant liposomes increases lung antioxidant activity in preterm rabbits (AJP 1995;269:L613). However, exogenous antioxidant enzymes may inhibit endogenous antioxidant enzyme synthesis. We treated preterm rabbits, born by cesarean section on day 28 of gestation, intratracheally with antioxidant-surfactant liposomes or air placebo at birth and exposed them to hyperoxia for 24 hours. Total lung RNA was isolated using the guanidinium thiocyanate-phenol-chloroform method, run on formaldehyde-agarose gels, and blotted onto nylon membranes. Rat lung CuZn-SOD cDNA (JCI 1989;83:1241) was used as a template for RNA transcription using SP6 RNA Polymerase and α[32P]CTP. CuZn-SOD cRNA (≈0.7 kb) was hybridized with total lung RNA, analyzed by autoradiography, and CuZn-SOD mRNA levels were quantified by densitometry. Total lung SOD activity in pups treated with antioxidant-surfactant liposomes was 72% higher than in air placebo controls, but lung CuZn-SOD mRNA quantities were similar in both groups. These data suggest that intratracheal instillation of CuZn-SOD does not affect its endogenous production in the fetal lung.