In vivo induction of prostasin mRNA in colonic epithelial cells by dietary sodium depletion and aldosterone infusion in rats.
BACKGROUND
Parallel induction of prostasin, a novel serine protease, together with epithelial sodium channel (ENaC) in the colon, may be essential for physiological response to increased circulating aldosterone. The aim of the present study was to investigate whether aldosterone induces prostasin mRNA in parallel with enhanced expression of ENaC in colonic epithelial cells.


METHODS
Sprague-Dawley rats were maintained on a sodium-depleted diet or subjected to continuous aldosterone infusion up to 4 weeks. Rats were necropsied at 1, 2, or 4 weeks after the beginning of each treatment. Blood was immediately collected and the large intestine was removed. Plasma aldosterone and arginine-vasopressin (AVP) levels were measured by radio-immunoassay. Epithelial cells were isolated from the right and left colon and RNA was extracted. Expression of prostasin and the alpha-, beta-, and gamma-subunits of ENaC was evaluated by quantitative RT-PCR or Northern blot analysis. In another series of experiments, T84 cells were stimulated with aldosterone, dexamethasone, and AVP alone or in combination, and prostasin mRNA was measured by quantitative RT-CPR.


RESULTS
Treatment with sodium-depleted diet and aldosterone infusion resulted in an increase of plasma aldosterone and induction of prostasin mRNA in the left colon. Expression of three subunits of ENaC also increased in the left colon. Induction of prostasin mRNA was observed when T84 cells were stimulated with corticosteroids plus AVP in vitro.


CONCLUSIONS
Aldosterone has a pivotal role for increasing expression of prostasin in epithelial cells of the left colon. AVP may have a synergistic effect on aldosterone-mediated prostasin induction.
Fukushima
Kouhei
K
Department of Surgery, Tohoku University, Graduate School of Medicine, 1-1 Seiryomachi, Aoba-ku, 980-8574, Sendai, Japan.
Naito
Hiroo
H
Funayama
Yuji
Y
Yonezawa
Hitoshi
H
Haneda
Sho
S
Shibata
Chikashi
C
Sasaki
Iwao
I
D000450:Aldosterone / Q000097:blood / Q000494:pharmacology*; D000818:Animals; D003106:Colon / Q000166:cytology* / Q000378:metabolism*; D004039:Diet, Sodium-Restricted; D004847:Epithelial Cells / Q000378:metabolism*; D053503:Epithelial Sodium Channels; D005786:Gene Expression Regulation; D008297:Male; D009481:Neurophysins / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012697:Serine Endopeptidases / Q000378:metabolism* / Q000502:physiology; D015222:Sodium Channels / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014667:Vasopressins / Q000378:metabolism; D000099271:Prostasin
D000450:Aldosterone; D053503:Epithelial Sodium Channels; D009481:Neurophysins; D011498:Protein Precursors; D012333:RNA, Messenger; D012697:Serine Endopeptidases; D015222:Sodium Channels; D014667:Vasopressins; D000099271:Prostasin; C438657:AVP protein, human