Expression of the Na+/H+ exchanger regulatory protein family in genetically hypertensive rats.
OBJECTIVE
To examine a possible involvement of a regulatory protein of Na+/H+ exchanger (NHE) in the increased renal NHE activity in spontaneously hypertensive rats (SHR), we investigated mRNA expression of inhibitory members of the NHE regulatory protein family, NHERF1 and NHERF2, in the kidney.


METHODS
Prehypertensive 4-week-old and hypertensive 11-week-old SHR and age-matched Wistar-Kyoto (WKY) rats were used to determine the changes in NHE activity and NHERF family expression in the kidney. Dahl salt sensitive (DS) and resistant rats were also used to examine whether these changes are specific for SHR.


METHODS
mRNA expression in the kidney was quantified by RNase protection assay. The NHE activity in primary cultured proximal tubular cells was measured as Na-dependent pHi recovery rate by the NH4Cl prepulse technique with 2'7'-bis-(2-carboxyethyl)-5.6-carboxyfluorescein (BCECF).


RESULTS
NHERF1 mRNA expression was significantly decreased in both prehypertensive and hypertensive SHR in comparison with age-matched WKY rats, whereas NHERF2 mRNA expression was significantly increased in SHR only in the hypertensive period. Antihypertensive treatment did not abolish these changes seen in control SHR. On the other hand, hypertensive DS rats fed a high-salt diet showed significant decreases in NHE activity and NHE3 mRNA expression compared with normotensive DS rats fed a low-salt diet, without significant changes in NHERF1 and NHERF2 mRNA expression.


CONCLUSIONS
These results suggest that decreased expression of NHERF1 may be related to the enhanced NHE activity in SHR and that these changes are likely to be genetically determined, whereas the increased NHERF2 expression may be induced as a compensatory mechanism.
Department of Internal Medicine, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
Kazuo
K
Kobayashi
Toshiaki
T
Monkawa
Matsuhiko
M
Hayashi
Takao
T
Saruta
D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D006973:Hypertension / Q000188:drug therapy / Q000503:physiopathology*; D008297:Male; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D020303:Rats, Inbred Dahl; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D000074082:Sodium-Hydrogen Exchanger 1; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics* / Q000378:metabolism
D000959:Antihypertensive Agents; D003598:Cytoskeletal Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; C452850:Slc9a1 protein, rat; C000613387:Slc9a3 protein, rat; C498832:Slc9a3r2 protein, rat; D000074082:Sodium-Hydrogen Exchanger 1; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor