The comparative assessment of nuclear run on of hydrophilic and hydrophobic surfactant protein by administration of steroid

Kim, Mi Ok; Kim, Tae Hyung; Sohn, Jang Won; Yoon, Ho Joo; Shin, Dong Ho; Park, Sung Soo

Abstract

BACKGROUND: Surfactant proteins are important in the regulation of the surfactant secretion, synthesis and recycling. Glucocorticoids are known to have primary or secondary effects on gene expression and can alter the rate of gene transcription. The hydrophilic and hydrophobic surfactant protein have been shown to be upregulated by glucocorticoids in vitro but its regulation in vivo, however, is not well established. The authors carried out nuclear run on assays to determine wheather glucocorticoids altered the transcription rate of SP-A, SP-B and SP-C genes.
METHODS
Adult rats were given the 2 mg/kg dose of subcutaneous dexamethasone for 2 days and sacrified at 2 days. The transcription rate of SP-A, SP-B and SP-C genes were measured by nuclear run on assays.
RESULTS
Treatment with 2 mg/kg dexamethasone increased transcription of SP-A gene (1.6-fold) and SP-C gene (1.3-fold) compared to the control for SP-A and SP-C after 2 days, which were not statistically significant. The rate of gene transcription for SP-B at 2 days after 2 mg/kg dexamethasone administration was significantly increased by 5.3-fold compared to the control for SP-B (p<0.005). The rates of gene transcription for hydrophilic and hydrophobic surfactant proteins, even in the hydrophobic surfactant proteins SP-B and SP-C were different.
CONCLUSIONS
The authors conclude that the difference in dexamethasone sensitivity may indicate that the three surfactant protein genes contain glucocorticoid response elements with different affinities for receptor in vivo.