Renal haemodynamic changes, renal tubular function, sodium and water homeostatic hormones in patients with chronic glomerulonephritis and in healthy humans after intravenous infusion of amino acids.

To determine whether renal reserve capacity was preserved in patients with chronic glomerulonephritis with well-preserved kidney function, and how sodium was handled in proximal and distal tubules, 13 healthy control subjects and 13 patients with biopsy-verified chronic glomerulonephritis were studied before and during a continuous 120-min amino-acid infusion. Glomerular filtration rate (GFR), renal plasma flow (RPF), and tubular function evaluated by the lithium clearance method, were determined during six clearance periods of 30 min each. Plasma concentrations of angiotensin II, atrial natriuretic peptide (ANP), aldosterone, arginine vasopressin (AVP), glucagon, amino acid and serum osmolality were determined before, 60, and 120 min after infusion. GFR and RPF increased about 10% in both groups; filtration fraction (FF) was unchanged. Proximal tubular reabsorption of sodium and water decreased, and distal tubular reabsorption of sodium and water increased, and thus the net excretion of sodium and water was unchanged. Angiotensin II and aldosterone were reduced in control subjects, but not in the patients. ANP and glucagon increased equally in both groups. Most amino acids increased two- or threefold. It is concluded that renal reserve capacity and glomerulotubular balance are intact in patients with chronic glomerulonephritis with well-preserved renal function, but there is an abnormal lack of suppression of the renin-angiotensin-aldosterone system in response to an amino acid infusion in these patients.