Renal hemodynamic response to intravenous and oral amino acids in animals.
Oral or parenteral application of amino acids leads to marked hyperfiltration and increased of renal plasma flow. Amino acids stimulate the release of glucagon, which increases hepatic production and release of cyclic adenosine monophosphate (cAMP). In the kidney, the combined effect of cAMP and glucagon increases glomerular filtration rate (GFR), possibly by reducing NaCl concentration at the macula densa and depression of the tubuloglomerular feedback. Vasopressin-dependent urea recycling and delivery to the thick ascending limb could similarly reduce NaCl concentration at the macula densa. Beyond that, amino acids may trigger a hepatorenal reflex or directly interfere with renal function. Mechanisms invoked include dopamine from renal nerves, prostaglandins, nitric oxide (NO), and angiotensin II. At this point, it is not clear to which extent the described mechanisms participate in, permit, or fully account for the hyperfiltrative effect of amino acids.