The American journal of physiology
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Increases of plasma arginine vasopressin (AVP) and plasma renin activity (PRA) during controlled mechanical ventilation (CMV) with positive end-expiratory pressure (PEEP) induce positive fluid balances by decreasing renal excretion. We investigated whether elevated levels of AVP and/or PRA maintain mean arterial pressure (MAP) during PEEP under conditions where plasma volume is not expanded. Six conscious chronically tracheotomized beagle dogs, kept under standardized conditions, were investigated in four protocols. ⋯ Neither MAP nor GFR changed during PEEP in control experiments in which both PRA and AVP increased, in AVPA experiments in which PRA increased, or in ACEI experiments in which AVP increased. We conclude that both AVP and angiotensin II contribute to the maintenance of MAP and GFR during PEEP. When both hormones are inhibited, no immediate compensation exists to prevent an acute fall in MAP and GFR.