Dexamethasone enhances surfactant protein gene expression in streptozotocin-induced immature rat lungs.
Because surfactant protein (SP) mRNA levels in rat fetuses are increased by maternal dexamethasone (dex) treatment and decreased in streptozotocin-induced diabetic (STZ-DB) pregnancy, we investigated the in vivo effects of dex on SP gene expression in STZ-DB pregnancy. The mRNA levels of SP (SP-A, SP-B, SP-C) were assessed in d 18 and 20 fetuses by Northern blot analysis, and nuclear run-on assays were performed with lung nuclei from d 20 fetuses (term = 22 d). Our findings indicate: 1) dex causes a greater increase in SP-A and SP-B mRNA levels in d 18 (12-16-fold) compared with day 20 (4-6-fold) fetuses (p < 0.05) in normal and STZ-DB pregnancy; 2) a 2-3-fold increase in SP-C mRNA levels was observed in response to dex in d 18 and 20 fetuses; 3) the increase in transcription of SP-A and SP-B in d 20 fetuses after dex is 68 and 60%, respectively, of the increase in their mRNA levels whereas in STZ-DB, the decrease in transcription compared with mRNA levels is 3.67-fold for SP-A and 2.42 fold SP-B; and 4) changes in SP-C transcription in either in vivo model, dex-treated or STZ-DB, correspond well with changes in mRNA levels. Together, these findings indicate that dex can enhance SP expression in STZ-DB immature lungs and support differential regulation of fetal SP genes in the models studied.
Rayani
H H
HH
Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, USA.
Warshaw
J B
JB
Floros
J
J
D000818:Animals; D003907:Dexamethasone / Q000494:pharmacology*; D003921:Diabetes Mellitus, Experimental / Q000139:chemically induced / Q000378:metabolism*; D005314:Embryonic and Fetal Development / Q000187:drug effects; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D008171:Lung Diseases / Q000139:chemically induced / Q000378:metabolism*; D008431:Maternal-Fetal Exchange; D009929:Organ Size / Q000187:drug effects; D011247:Pregnancy; D011254:Pregnancy in Diabetics / Q000378:metabolism*; D011663:Pulmonary Surfactants / Q000235:genetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014158:Transcription, Genetic / Q000187:drug effects
D011663:Pulmonary Surfactants; D003907:Dexamethasone