Altered Renal Response Following an Amino Acid Infusion in Essential Hypertension.

To assess the clinical implications of protein load in essential hypertension, we measured renal plasma flow (RPF) and glomerular filtration rate (GFR) at 30-min intervals after initiating 10% amino acid infusion (6.7mg/kg/min for 30min) in 10 untreated patients with essential hypertension and 8 subjects with normotension. Amino acids provoked significant and equivalent renovasodilation without alteration of systemic hemodynamics in both hypertensive and normotensive groups (% change of RPF induced by amino acids: +12.8±3.0% in hypertensive vs. +15.3±4.4% in normotensive group). GFR also significantly increased in both groups, but the magnitude of this rise was lower in the hypertensive than in the normotensive group (+8.7±3.2% vs. +34.1±4.0%, p<0.01). Consequently, filtration fraction did not change following the amino acid infusion in hypertensive patients (0.28±0.01 to 0.27± 0.02, ns), whereas it significantly increased in normotensive subjects (0.23±0.02 to 0.27±0.02, p< 0.01). Amino acids also increased plasma glucagon to a comparable level (120.6±14.5pg/ml in hypertensive vs. 101.1±14.8pg/ml in normotensive group) in both groups, and this level was correlated with the degree of hyperfiltration induced by amino acids in the normotensive group (r=0.79, p< 0.05). In conclusion, renal functional reserve estimated by the increase in GFR following the amino acid infusion was lower in the hypertensive than in the normotensive group. This abnormality found in essential hypertension might be related to enhanced responsiveness of efferent arterioles to the vasodilatory stimuli induced by amino acids. (Hypertens Res 1992; 15: 77-84)