Central role of angiotensin in the hyperosmolality- and hypovolaemia-induced vasopressin release in conscious rats.
To evaluate a central role of angiotensin in vasopressin (ADH) release in response to hyperosmolality or hypovolaemia, we examined in conscious rats the effects of intraperitoneal (ip) injections of 2 ml/100 g body weight of hypertonic saline or polyethylene glycol (PEG; 250 mg/ml of 145 mM NaCl) on plasma ADH and angiotensin II (AII) levels and of intracerebroventricular (icv) administrations of Sar1-Ala8-AII (a competitive receptor blocker for AII) on the plasma ADH responses to the ip injections. Thirty min after ip injections of 900 mM NaCl, plasma ADH, osmolality and sodium increased with unchanged plasma AII and with reduced haematocrit. Two h after ip administrations of PEG, plasma ADH, AII and haematocrit were augmented with unaltered plasma osmolality and sodium. The responses of plasma ADH to ip injections of 900 mM NaCl and PEG were significantly inhibited (P less than 0.05) by 1 microgram of Sar1-Ala8-AII injected icv 5 min before blood samplings which had no appreciable effect on plasma osmolality, electrolytes and haematocrit. Based on these results, we concluded that angiotensin may participate in both the hyperosmolality- and hypovolaemia-induced ADH secretion by acting on the central nervous system.
D000804:Angiotensin II / Q000097:blood*; D000818:Animals; D001127:Arginine Vasopressin / Q000097:blood*; D001810:Blood Volume / Q000187:drug effects*; D001921:Brain / Q000187:drug effects; D008297:Male; D009994:Osmolar Concentration; D011092:Polyethylene Glycols / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012462:Saline Solution, Hypertonic / Q000494:pharmacology; D012504:Saralasin / Q000494:pharmacology
D012462:Saline Solution, Hypertonic; D000804:Angiotensin II; D001127:Arginine Vasopressin; D011092:Polyethylene Glycols; D012504:Saralasin