title: Blood pressure maintenance in awake dehydrated rats: renin, vasopressin, and sympathetic activity.
abstract: The role of vasopressin, the renin system, and sympathetic activity in sustaining blood pressure in the dehydrated state was investigated in normotensive nonanesthetized male Wistar rats. After 48-h dehydration, plasma arginine vasopressin was 14.0 +/- 1.7 pg/ml and plasma norepinephrine 0.46 +/- 0.05 ng/ml. In another group of rats in which the angiotensin converting enzyme inhibitor (MK 421, 5 mg po twice daily) was administered throughout the dehydration period, blood pressure was reduced by more than 20% (P less than 0.001), and both plasma arginine vasopressin and norepinephrine were higher at 23.4 +/- 3.9 pg/ml (P less than 0.01) and 0.83 +/- 0.07 ng/ml (P less than 0.01), respectively. Taken together, in rats with or without converting enzyme blockade, there was an inverse correlation between mean blood pressure and plasma arginine vasopressin (r = 0.67, P less than 0.01) as well as plasma norepinephrine (r = 0.82, P less than 0.01) levels. The acute administration of a specific vasopressin pressor inhibitor (dPVDAVP) reduced mean blood pressure in the rats with a blocked renin system by 16.9 mmHg (P less than 0.001). In rats without converting enzyme inhibition, the induced fall was only 6.4 mmHg. These results indicate that following 48-h dehydration the renin angiotensin system interacts with the vasopressin secretory mechanism to sustain blood pressure, with renin playing a predominant role. They further suggest that, following blockade of the renin system, activation of the sympathetic nervous system probably also contributes to blood pressure maintenance.
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors; D000818:Animals; D001127:Arginine Vasopressin / Q000097:blood*; D001794:Blood Pressure / Q000187:drug effects; D003681:Dehydration / Q000503:physiopathology*; D004151:Dipeptides / Q000494:pharmacology; D004656:Enalapril; D004837:Epinephrine / Q000097:blood; D006339:Heart Rate / Q000187:drug effects; D008236:Lypressin / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000097:blood*; D007703:Peptidyl-Dipeptidase A / Q000097:blood; D051381:Rats; D011919:Rats, Inbred Strains; D012083:Renin / Q000097:blood*; D014851:Wakefulness / Q000502:physiology*
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D004151:Dipeptides; D001127:Arginine Vasopressin; D008236:Lypressin; D004656:Enalapril; D007703:Peptidyl-Dipeptidase A; D012083:Renin; D009638:Norepinephrine; D004837:Epinephrine