[Contribution of endothelin and its receptors to ouabain-induced hypertension in rats].
OBJECTIVE
To investigate the effect of endothelin and its receptors on ouabain-induced hypertension in rats.


METHODS
Male Sprague-Dawley (SD) rats were treated with ouabain or saline for 6 weeks and their systolic blood pressure (SBP) were recorded weekly. At the end of 2, 4 and 6 weeks, respectively, the plasma and left ventricle endothelin contents were measured by radio-immunoassay, and real-time quantitative RT-PCR was employed to determine the mRNA level of endothelin type A receptor (ETAR) and type B receptor (ETBR) in the left ventricle, and the protein expressions of ETAR and ETBR were examined by immuno-histochemistry.


RESULTS
After 4 weeks of intraperitoneal ouabain injection, the mean SBP in ouabain group increased till reaching a level significantly higher than that in the control group after 6 weeks (P<0.001). The plasma and left ventricle endothelin contents were significantly increased after 2 weeks of ouabain injection (P<0.01), and similarly, increased ETAR mRNA was observed. After 4 weeks of treatment, ETAR mRNA was increased continuously and the protein expression of ETAR upregulated in ouabain group as compared with the control group. The transcription and protein expression of ETBR were not altered by ouabain treatment.


CONCLUSIONS
Before detectable blood pressure elevation occurs, endothelin concentration and ETAR can be already upregulated in ouabain-induced hypertensive rats, suggesting that endothelin might be involved in the cardiovascular effects of ouabain via an action on ETAR.
Jiang
Xin
X
Department of Geriatric Cardiology, First Hospital of Xi'an Jiaotong University, Xi'an 710061, China. jiangxinwind@126.com
Guo
Ning
N
Lü
Zhuo-ren
ZR
D000818:Animals; D016232:Endothelins / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics; D006973:Hypertension / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D009206:Myocardium / Q000378:metabolism; D010042:Ouabain; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D044022:Receptor, Endothelin A / Q000235:genetics / Q000378:metabolism; D044023:Receptor, Endothelin B / Q000235:genetics / Q000378:metabolism; D017466:Receptors, Endothelin / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D016232:Endothelins; D012333:RNA, Messenger; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; D010042:Ouabain