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 inpatients with chronic glomerulonephritis with well-preservedkidney function, and how sodium was handled in proximal anddistal tubules, 13 healthy control subjects and 13 patientswith biopsy-verified chronic glomerulonephritis were studiedbefore and during a continous 120-min amino-acid infusion. Glomerularfiltration rate (GFR), renal plasma flow (RPF), and tubularfunction evaluated by the lithium clearance method, were determinedduring six clear ance periods of 30 min each. Plasma concentrationsof angiotensin II, atrial natriuretic peptide (ANP), aldosterone,arginine vasopressin (AVP), glucagon, amino acid and serum osmolalitywere determined before, 60, and 120 min after infusion. GFRand RPF increased about 10% in both groups; filtration fraction(FF) was unchanged. Proximal tubular reabsorption of sodiumand water decreased, and distal tubular reabsorption of sodiumand water increased, and thus the net excretion of sodium andwater was unchanged. Angiotensin II and aldosterone were reducedin control subjects, but not in the patients. ANP and glucagonincreased equally in both groups. Most amino acids increasedtwo- or threefold. It is concluded that renal reserve capacityand glomerulotubular balance are intact in patients with chronicglomerulonephritis with well-preserved renal function, but thereis an abnormal lack of suppression of the renin-angiotensin-aldosteronesystem in response to an amino acid infusion in these patients.