Effects of intraventricular injection of Sar1-Ala8-angiotensin II on plasma vasopressin level increased by angiotensin II and by water deprivation in conscious rats.
The effects of intraventricular injection of Sar1-Ala8-angiotensin II (A specific antagonist of angiotensin II) on the plasma vasopressin level increased by intraventricular injection of angiotensin II and by water deprivation (46 h) were examined in conscious male rats with an indwelling cannula in the third cerebral ventricle. Blood samplings were made by decapitation and the plasma level of vasopressin was determined by radioimmunoassay. Twenty-five, 50 or 100 ng of angiotensin II produced significant (P less than 0.05) increase in plasma vasopressin level 90 sec after the injection. The effect of 50 ng of angiotensin II was inhibited significantly (P less than 0.05) at least with 100 ng of Sar1-Ala8-angiotensin II given 2 min before the injection of angiotensin II. The dehydrated rats to which 1000 ng of Sar1-Ala8-angiotensin II was given 5 min before the decapitation showed the significantly (P less than 0.05) lower median plasma vasopressin level than that of the dehydrated controls. No significant difference in plasma osmolality was noted between them. These results suggest that the plasma vasopressin response to intraventricular angiotensin II is produced via angiotensin II receptors in the brain and that Sar1-Ala8-angiotensin II inhibits the effect of endogenous angiotensin II on plasma vasopressin level under dehydration.
D000804:Angiotensin II / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000818:Animals; D003681:Dehydration / Q000097:blood*; D007276:Injections, Intraventricular; D008297:Male; D051381:Rats; D012504:Saralasin / Q000008:administration & dosage / Q000494:pharmacology; D014667:Vasopressins / Q000097:blood*
D014667:Vasopressins; D000804:Angiotensin II; D012504:Saralasin