Effect of arginine vasopressin on urine formation and plasma atrial natriuretic peptide level in conscious dogs.

We investigated the relationship between plasma arginine vasopressin (AVP) and atrial natriuretic peptide (ANP) levels and urine formation in conscious dogs. The rate of urine production and urinary electrolyte excretion were determined following infusion of high doses of AVP to dogs in different volume states. Water deprivation for 24 h induced an antidiuresis while the plasma osmolality, plasma AVP and plasma ANP remained at physiological levels. Subsequent i.v. administration of AVP did not alter the production of urine. Oral water loading (20 ml/kg body weight) induced low plasma AVP levels (1.3 +/- 0.5 pg/ml, mean +/- S.E.M.). Following AVP administration to the water-loaded group, the urine production rate decreased significantly from baseline while the osmolality of the urine increased significantly. Plasma ANP levels did not differ significantly between the two experimental groups, and did not change following i.v. administration of AVP. The results show that, in conscious dogs, (1) the production of a small volume of highly concentrated urine can occur with plasma AVP levels of below 5 pg/ml, (2) 24 h of dehydration induces an antidiuresis while plasma peptides, as well as the different biochemical variables, remain within normal limits, (3) increased plasma AVP levels do not induce a change in plasma ANP levels under these experimental conditions, (4) infusion of AVP induces a significantly increased K+ excretion but only in overhydrated animals.