Relationship of renin-angiotensin system and ET-1 system activation in long-lasting response to postural changes.
The present study was performed in seven healthy subjects (aged 22-35 years) to investigate 1) whether plasma and urinary endothelin-1 (ET-1) are involved in the response to postural changes and 2) the relationship between ET-1 formation and the renin-angiotensin system (RAS). Six hours of standing caused a prompt but very short-lasting increase in plasma ET-1 concentration (59% after 5 min, 12% after 1 h) and a notable and sustained enhancement of urinary ET-1 excretion (from 0.59 +/- 0.10 to 1.43 +/- 0.28 pg/min, or 142%; P < 0.001). Plasma renin activity increased by 169% after 1 h of standing. A parallel contraction of urinary volume (-62%), sodium excretion (-55%), and free water reabsorption (-24%) occurred. The return to the supine position after 6 h of orthostasis caused a reduction to baseline values of the ET-1 urinary excretion and urinary volume within 2 h. Inhibition of angiotensin-converting enzyme blunted, but did not eliminate, the orthostasis-induced increase in ET-1 urinary excretion (100%, P < 0.002) and changes in the renal functions. The present results indicate that renal ET-1 is involved in the hemodynamic long-lasting responses to postural changes and that its increase is partially controlled by RAS and suggest that ET-1 might play a role in the regulation of renal function in humans.
Modesti
P A
PA
Clinica Medica I, University of Florence, Italy.
Cecioni
I
I
Naldoni
A
A
Migliorini
A
A
Neri Serneri
G G
GG
D000042:Absorption; D000328:Adult; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D019332:Endothelin-1 / Q000097:blood / Q000502:physiology* / Q000652:urine; D005260:Female; D006801:Humans; D007668:Kidney / Q000378:metabolism / Q000502:physiology; D008297:Male; D009994:Osmolar Concentration; D011187:Posture / Q000502:physiology*; D017257:Ramipril / Q000494:pharmacology; D012083:Renin / Q000097:blood; D012084:Renin-Angiotensin System / Q000502:physiology*; D016683:Supine Position; D013997:Time Factors; D014556:Urine / Q000502:physiology; D014867:Water / Q000378:metabolism
D000806:Angiotensin-Converting Enzyme Inhibitors; D019332:Endothelin-1; D014867:Water; D012083:Renin; D017257:Ramipril