Korean J Aerosp Environ Med.  2003 Dec;13(4):184-189.

Changes in Renal Expression of Natriuretic Peptides and Their Receptors mRNA Induced by Head-down Suspension in Rats

• Bae JH
• Hwang JS

Abstract

BACKGROUND
Head-down suspension (HDS) of rats has been used as a model for the simulation of a microgravity environment. Atrial natriuretic peptide (ANP), C-type natriuretic peptides (CNP) and their receptors are found in the kidney, suggesting that these peptides could play a significant physiological role in the kidney. Therefore, this study was investigated the changes in the adaptations of renal natriuretic peptides and their receptors syntheses after 4 weeks of HDS in rats.
METHODS
Unanesthetized, unrestrained, male Sprague-Dawley rats were subjected to either a horizontal position (control rats) or a -45degreeshead-down tilt using the tail-traction technique (HDS rats). This study observed the renal syntheses of natriuretic peptides as a expression of ANP and CNP mRNA, and also determined the expression of A-type natriuretic peptide receptor (NPR-A) mRNA and B-type NPR (NPR-B) mRNA. The expressions of natriuretic peptide and NPR mRNA were measured by reverse transcription-polymerase chain reaction with [(32)P]-dCTP following 4 weeks of HDS in the kidney of both control and HDS rats.
RESULTS
After 4 weeks of HDS, the expression of ANP mRNA significantly (P<0.01) decreased, while CNP mRNA expression was showed the non-significant increasing trend in the kidney of HDS rats. NPR-A, which binds with ANP, was significantly (P<0.001) decreased in renal mRNA expression of HDS rats compared with controls. Expression in mRNA of NPR-B, which binds with CNP, showed a slightly decreasing trend in the kidney of rats following HDS.
CONCLUSION
These results suggest that the renal adaptation following 4 weeks of HDS exerts to maintain the blood volume and electrolyte balance through attenuation of syntheses in the natriuretic peptide and its binding receptor, especially in ANP rather than in CNP systems.

Keyword

Head-down suspension; ANP; CNP; Natriuretic peptide receptor; mRNA; Kidney

MeSH Terms

Animals
Atrial Natriuretic Factor
Blood Volume
Humans
Kidney
Male
Natriuretic Peptides*
Peptides
Rats*
Rats, Sprague-Dawley
Receptors, Peptide
RNA, Messenger*
Water-Electrolyte Balance
Weightlessness
Atrial Natriuretic Factor
Natriuretic Peptides
Peptides
RNA, Messenger
Receptors, Peptide