Characterization of gastric Na+/I- symporter of the rat.
Characterization of gastric Na+/I- symporter (NIS) of the rat was carried out. Sequencing of the open reading frame of gastric NIS mRNA showed only three nucleotide changes when compared with FRTL-5 NIS cDNA, and two of these changes led to amino acid changes. The results of Northern blot analysis showed that abundant NIS mRNA was expressed in the stomach when compared with other organs. Western blot analysis using gastric mucosa and FRTL-5 lysates detected the difference in molecular weight between FRTL-5 and gastric mucosa lysates, suggesting abnormal posttranslational modification of gastric NIS protein. Immunohistochemically, gastric NIS protein was located in the cornification layer of the stratified squamous epithelium of the pars proventricularis and in parietal cells and on the apical border of surface epithelial cells of the pars glandularis. Gastric NIS protein was present in tubulovesicular structures and lysosomes in parietal cells by immunoelectron microscopy. Gastric NIS protein exists to trap I- from the gastric lumen, except in parietal cells. Results indicated that a very large amount of gastric NIS mRNA is expressed to be translated, whereas only a small amount of immature gastric NIS protein is detected. This may indicate that immature gastric NIS protein rapidly degrades to peptides.
Kotani
T
T
Department of Laboratory Medicine, Miyazaki Medical College, Japan.
Ogata
Y
Y
Yamamoto
I
I
Aratake
Y
Y
Kawano
J I
JI
Suganuma
T
T
Ohtaki
S
S
D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D005260:Female; D005753:Gastric Mucosa / Q000378:metabolism* / Q000648:ultrastructure; D015870:Gene Expression; D007454:Iodides / Q000378:metabolism*; D017136:Ion Transport; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D016253:Microscopy, Immunoelectron; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012964:Sodium / Q000378:metabolism*; D027981:Symporters; D014018:Tissue Distribution; D014162:Transfection; D000099209:Sodium-Iodide Symporters
D002352:Carrier Proteins; D017931:DNA Primers; D007454:Iodides; D008565:Membrane Proteins; D012333:RNA, Messenger; D012964:Sodium; D027981:Symporters; D000099209:Sodium-Iodide Symporters