A role for Na/K adenosine triphosphatase in the pathogenesis of cyst formation in experimental polycystic kidney disease.
Multiple cyst formation with fluid retention is a characteristic structural abnormality in polycystic kidney disease (PKD). Na/K adenosine triphosphatase (ATPase) is a major transporting membrane protein that is ubiquitous in the epithelial cell, which has been thought to be involved in cystogenesis. We have investigated the molecular and histologic basis of Na/K ATPase activity in experimental PKD in vivo. Rats were treated with diphenylthiazole (100 mg/100 gm body weight), and cyst formation was examined histologically. Na/K ATPase activity was measured enzymatically by using a fluorometric method, and reverse transcription-competitive polymerase chain reaction (RT-PCR) analysis was used to quantitate mRNA levels in the isolated single nephron segment. Kidneys were immunostained with subunit-specific antibodies to determine the localization of Na/K ATPase in the epithelial cell. The enzyme activity increased in the cortical collecting duct from 25.9 +/- 3.5 mmol/Lpmol/mm/min to 72.9 +/- 6.8 pmol/mm/min and in the outer medullary collecting duct from 13.0 +/- 3.9 mmol/Lpmol/mm/min to 58.5 +/- 9.8 pmol/mm/min (n = 6, p < 0.01); however, all other segments showed no significant changes. No significant alternation in alpha 1- and beta 1-subunits of Na/K ATPase mRNA levels was observed by competitive PCR assay in either segment. The enzyme was stained at the basolateral membrane even in the cystic tubules. Na/K ATPase activity was up-regulated in the cyst-formed kidney, but this was not accompanied with transcriptional up-regulation. Increased Na/K ATPase activity at normal locations may play a role in abnormal net fluid transport in the development and progression of experimental PKD.
Takahashi
M
M
Department of Medicine, Tokyo Women's Medical College, Japan.
Tsuchiya
K
K
Komatsu
Y
Y
Nihei
H
H
D000818:Animals; D017931:DNA Primers / Q000737:chemistry; D004848:Epithelium / Q000201:enzymology / Q000473:pathology; D007124:Immunoenzyme Techniques; D007684:Kidney Tubules / Q000201:enzymology / Q000473:pathology; D008029:Lighting; D008297:Male; D007690:Polycystic Kidney Diseases / Q000139:chemically induced / Q000201:enzymology* / Q000209:etiology* / Q000473:pathology; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism*; D013844:Thiazoles
D017931:DNA Primers; D012333:RNA, Messenger; D013844:Thiazoles; D000254:Sodium-Potassium-Exchanging ATPase