ABSTRACT
The Na(+) pump, Na(+)-K(+)-ATPase, along with the Na(+) channel is essential for the removal of alveolar solute and fluid perinatally. Because Na(+)-pump mRNA and activity increase before birth and maternal glucocorticoids (GCs) influence Na(+)-K(+)-ATPase mRNA expression in fetal rat lung, we hypothesized that GCs increased Na(+)-K(+)-ATPase gene expression in a fetal lung epithelial cell line. After 24 h of exposure, dexamethasone increased the steady-state levels of Na(+)-K(+)-ATPase alpha(1) and beta(1) mRNA in a fetal rat lung epithelial cell line in a dose-dependent fashion (10(-7) to 10(-5) M). The maximal increase in mRNA levels was 3. 8-fold for alpha(1) and 2.8-fold for beta(1). The increase in mRNA was detected as early as 6 h for the beta(1)-subunit and 18 h for the alpha(1)-subunit, and both peaked at 24 h. This gene upregulation was not due to increased mRNA stability based on mRNA half-life determination after actinomycin D inhibition. Transfection experiments with alpha(1) and beta(1) promoter-reporter constructs demonstrated 3.2 +/- 0.5- and 2.6 +/- 0.4-fold increases, respectively, in promoter activity, consistent with transcriptional activation of the promoter-reporter construct. These findings, increased promoter activity with no change in stability, indicate that GCs increased Na(+)-K(+)-ATPase transcription in a fetal lung epithelial cell line.
Subject(s)
Dexamethasone/pharmacology , Gene Expression Regulation/drug effects , Glucocorticoids/pharmacology , Lung/embryology , Sodium-Potassium-Exchanging ATPase/genetics , Animals , Cell Line , Epithelium/embryology , Fetus/cytology , Fetus/enzymology , Fetus/physiology , Half-Life , Homeostasis/physiology , Promoter Regions, Genetic/drug effects , Promoter Regions, Genetic/physiology , RNA, Messenger/metabolism , RatsABSTRACT
11C-benzoic acid prepared in a radiochemical purity over 90% was studied radiopharmacologically in mice and rabbits. The uptake of 11C-benzoate in ICR mice increased quickly. The ratio of kidney uptake rate to that in other organs reached values between 9 and 55 with a maximum at 10 min after i.v. injection. Gamma camera imaging of rabbits showed that uptake in the kidneys began at 2 min after injection and that activity began to appear in the bladder 4 min later. Rabbits with left renal artery ligature showed no uptake in the left kidney but the right kidney was imaged to the same extent as that of a rabbit without artery ligature. The kidney imaging of 11C-benzoic acid may be a useful method for renal diagnosis.
