AJP - Endocrinology and Metabolism, Vol 245, Issue 6 611-E615, Copyright © 1983 by American Physiological Society
Splanchnic clearance of plasma vasopressin in the dog: evidence for prehepatic extraction
K. Matsui, L. Share, D. P. Brooks, J. T. Crofton and R. W. Rockhold
It is generally considered that the liver is primarily responsible for the
extraction of vasopressin from the circulating blood by the splanchnic
viscera. To investigate this matter further, measurements were made in the
anesthetized dog of the concentrations of vasopressin in arterial, portal
venous, and hepatic venous plasma, and of total splanchnic plasma flow and
hepatic arterial plasma flow. The total splanchnic vasopressin extraction
ratio was 12.9 +/- 1.0%. However, the concentration of vasopressin in
portal venous plasma was consistently lower than in arterial plasma, and
there was a substantial prehepatic extraction of vasopressin, averaging
10.5 +/- 0.8%. A quantitative evaluation of the contribution of the
"prehepatic" viscera, i.e., viscera with venous drainage into the portal
vein, is provided by the relevant clearances of vasopressin. The prehepatic
and total splanchnic vasopressin clearances were 1.58 +/- 0.20 and 3.04 +/-
0.31 ml X min-1 X kg-1, respectively. Thus, the splanchnic viscera other
than the liver were responsible for approximately half of the splanchnic
clearance of vasopressin; the remainder could be attributed to the liver.
Immunoreactive vasopressin was not found in the bile. In splenectomized
dogs, in which venous blood was collected from the superior mesenteric
vein, the vasopressin extraction ratio was 14.6 +/- 2.3%, suggesting that
the prehepatic clearance of vasopressin occurs largely in the mesenteric
bed. A more specific localization of the prehepatic clearance sites has not
as yet been made.
