CONTRIBUTION OF ANP TO PLASMA-PROTEIN ESCAPE DURING VE - EFFECTS OF THIORPHAN AND ATRIAL APPENDECTOMY

The effects of endopeptidase inhibition and right atrial appendectomy (AA) on plasma immunoreactive atrial natriuretic peptide (irANP) conce ntrations and extravascular accumulation of I-131-labeled bovine serum albumin (C-BSA) during volume expansion (VE) were examined in pentoba rbital sodium-anesthetized rats (n=5 per group). Compared with control s, infusion of isoncotic albumin (30 ml/kg) increased central venous p ressure (CVP) by 5.5 mmHg, plasma irANP by 7-fold, and C-BSA in multip le tissues by 1.6- to 4-fold (P less than or equal to 0.05). Inhibitio n of ANP metabolism with thiorphan (40 mg/kg) had no effect in control animals but increased plasma irANP (+118%) and C-BSA (+30-100%) compa red with VE alone (P less than or equal to 0.05). Likewise, interferen ce with ANP release by AA reduced plasma irANP (-80%) and C-BSA (-30 t o -80%) response to VE in parallel (P less than or equal to 0.05). The peak increase in CVP during VE was not affected by either of these ma nipulations. It is concluded that endogenous ANP increases plasma prot ein extravasation independent of volume and pressure disturbances duri ng acute intravascular expansion.