ARTICLES

Arginine vasopressin metabolism in dogs. I. Evidence for a receptor-mediated mechanism

The plasma clearance rates (PCR) of arginine vasopressin (AVP), and iodinated AVP (125I-AVP) were determined after pulse injection in conscious water-loaded dogs. Both the PCR and the apparent initial volume of distribution were significantly greater for AVP than for the biologically inactive iodinated AVP 37.4 +/- 4.8 ml/kg per min vs. 6.7 +/- 0.8 ml/kg per min (P less than 0.001) and 12.7 +/- 0.9% body wt vs. 7.1 +/- 0.4% body wt (P less than 0.001). AVP clearance was then determined by the constant-infusion technique at doses that produced equilibrium AVP concentrations within and above the physiological range. AVP-PCR was 37.4 +/- 7.1 ml/kg per min at 34 microU/kg per min, which was comparable to that after pulse injection (P less than 0.9). AVP clearance fell progressively, and urine osmolality progressively increased with increasing AVP infusion rates to plateau values at 136 microU/kg per min; a strong negative correlation was observed between mean AVP-PCR and urine osmolality (r = -0.993). The data suggest a relationship between the biological activity of AVP and its clearance. It is proposed that plasma membrane receptors may mediate a portion of the metabolic clearance of AVP.