Role of the liver in renal hemodynamic response to amino acid infusion.

The purpose of this study is to determine the quantitative importance of the liver in mediating the increases in renal blood flow and glomerular filtration rate (GFR) that occur after elevation of plasma amino acids. A mixture of four amine acids (Gly, Ser, Ala, Pro at 0.075 mmol X kg-1 X min-1 total) was infused intravenously into normal anesthetized dogs and into a second group of dogs after ligating all blood vessels supplying the liver and inserting a hepatic portal-femoral venous shunt. In normal dogs, renal blood flow and GFR rose by an average of 20 +/- 3 and 15 +/- 4%, respectively, after 30 min of amino acid infusion, while renal vascular resistance fell 16% from 0.51 +/- 0.16 to 0.43 +/- 0.16 mmHg X ml-1 X min. The responses of dogs in which the hepatic circulation was ligated were not significantly different from those in normal animals; renal blood flow and GFR increased by 20 +/- 3 and 31 +/- 7%, respectively, and renal vascular resistance fell 26% from 0.80 +/- 0.13 to 0.59 +/- 0.08 mmHg X ml-1 X min after 30 min of amino acid infusion. Because ligation of the blood supply to the liver did not prevent the renal hemodynamic response to amino acid infusion, it appears that the liver does not play a major role in mediating renal vasodilation during elevation of plasma amino acids.