Vasopressin release induced by water deprivation: effects of centrally administered saralasin.
Uncertainty exists as to whether endogenous angiotensin activates brain mechanisms controlling vasopressin (AVP) secretion during dehydration. We injected various doses of saralasin into a lateral cerebroventricle (IVT) of conscious, male rats deprived of water for 48 h and killed them at different times. The concentration of AVP in the plasma (p[AVP]), measured by radioimmunoassay, was unaffected by saralasin. IVT pretreatment with 1-Sar-8-Ile-angiotensin II blocked maximal AVP release by IVT angiotensin, but this pretreatment did not reduce p[AVP] after 24, 48 or 72 h water deprivation. A 3-hour continuous IVT infusion of CSF or saralasin (10 micrograms/h) into 48-hour water-deprived rats revealed equivalent p[AVP] and urine volumes. When the infusions were continued for 3 h more with water available, control and saralasin-treated rats: (a) drank at similar rates, (b) excreted similar amounts of urine, and (c) reduced their p[AVP] levels to the same extent. IVT saralasin did not affect p[AVP] of rats dehydrated with hypertonic NaCl. Combined IVT saralasin and atropine reduced p[AVP] of 48-hour water deprived rats about 30% (p less than 0.05). We conclude that redundancy exists for sensing, integrating and releasing vasopressin in dehydrated rats.
D015059:1-Sarcosine-8-Isoleucine Angiotensin II / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D003681:Dehydration / Q000503:physiopathology; D004327:Drinking Behavior / Q000187:drug effects; D007276:Injections, Intraventricular; D008297:Male; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D012462:Saline Solution, Hypertonic; D012504:Saralasin / Q000494:pharmacology*; D014667:Vasopressins / Q000032:analysis / Q000097:blood / Q000378:metabolism*; D014868:Water Deprivation / Q000502:physiology*
D012462:Saline Solution, Hypertonic; D014667:Vasopressins; D001285:Atropine; D015059:1-Sarcosine-8-Isoleucine Angiotensin II; D012504:Saralasin