Increased expression of atrial natriuretic peptide in the kidney of rats with bilateral ureteral obstruction.
BACKGROUND
Whether the postobstructive diuresis can be related to an altered regulation of local atrial natriuretic peptide (ANP) in the kidney was investigated.


METHODS
Three groups of rats had both of their ureters obstructed for 48 hours. The kidneys were taken without releasing the obstruction in one group [bilateral ureteral obstruction (BUO)]. The obstruction was released in the other two groups and the animals were kept for 4 and 24 hours thereafter to collect urinary data (BUR-4 and BUR-24, respectively). Plasma and urine ANP levels were measured by radioimmunoassay. The mRNA expression of ANP, natriuretic peptide receptor-A (NPR-A), and NPR-C was determined by reverse transcription-polymerase chain reaction. ANP receptors were also quantitated by in vitro autoradiography. The activity of guanylyl cyclase was determined by the amount of cGMP generated in response to ANP.


RESULTS
Urinary volume and sodium excretion increased in BUR-4, along with the ANP mRNA expression in the kidney and the urinary ANP excretion. The ANP excretion positively correlated with the urinary volume and sodium excretion. The mRNA expression of both NPR-A and NPR-C was decreased by BUO, the latter being far more prominently affected. The maximal binding capacity of radiolabeled ANP was decreased in the glomerulus and papilla in BUO. Not only the urinary parameters but also the mRNA expression of ANP, NPR-A, and NPR-C were comparable between BUR-24 and control rats. ANP-stimulated cGMP generation was reduced in the glomerulus and papilla in BUO animals, which was rapidly resumed following the release of the obstruction.


CONCLUSIONS
Postobstructive diuresis may be due partially to an increased ANP activity in the kidney.
Kim
S W
SW
Chonnam University Research Institute of Medical Sciences and Hormone Research Center, Kwangju, Korea.
Lee
J
J
Park
J W
JW
Hong
J H
JH
Kook
H
H
Choi
C
C
Choi
K C
KC
D000818:Animals; D009320:Atrial Natriuretic Factor / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D001806:Blood Urea Nitrogen; D003404:Creatinine / Q000097:blood; D006162:Guanylate Cyclase / Q000378:metabolism; D008297:Male; D009318:Natriuresis; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017461:Receptors, Atrial Natriuretic Factor / Q000235:genetics; D013997:Time Factors; D014517:Ureteral Obstruction / Q000378:metabolism* / Q000503:physiopathology
D012333:RNA, Messenger; D009320:Atrial Natriuretic Factor; D003404:Creatinine; D006162:Guanylate Cyclase; D017461:Receptors, Atrial Natriuretic Factor