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Proximal tubular function and hyperfiltration during amino acid infusion in man
A Claris-Appiani1, B M Assael, A S Tirelli
1Clinica Pediatrica II, Università di Milano, Italia.
American Journal of Nephrology
|January 1, 1988
Summary
Amino acid infusions increased kidney blood flow and glomerular filtration rate, unlike saline infusions. Amino acids counteracted volume expansion effects on proximal sodium reabsorption, suggesting metabolic stimulation.
Area of Science:
- Nephrology
- Renal Physiology
- Cardiovascular Physiology
Background:
- Understanding the interplay between renal hemodynamics and sodium handling is crucial for managing fluid and electrolyte balance.
- Previous research indicates that extracellular volume expansion influences renal function, but specific mechanisms involving amino acids require further elucidation.
Purpose of the Study:
- To investigate the distinct effects of isotonic amino acid and saline infusions on renal hemodynamics and segmental sodium handling in healthy adults.
- To explore the potential role of amino acids in modulating proximal tubular sodium reabsorption during volume expansion.
Main Methods:
- Healthy adult subjects received infusions of either isotonic amino acid solution or 0.9% saline.
- Maximal water diuresis was induced to facilitate the analysis of sodium transport.
- Renal hemodynamics (glomerular filtration rate, renal blood flow) and segmental sodium handling (distal delivery, reabsorption, fractional excretion) were measured.
Main Results:
- Both infusions caused similar extracellular volume expansion, indicated by weight gain, hematocrit fall, and suppressed renin and aldosterone levels.
- Amino acid infusion significantly increased glomerular filtration rate and renal blood flow without altering filtration fraction.
- Saline expansion reduced both proximal and distal sodium reabsorption, while amino acid infusion maintained distal sodium delivery but increased fractional excretion due to reduced distal reabsorption.
Conclusions:
- Isotonic amino acid infusion induces renal vasodilation, increasing glomerular filtration rate and renal blood flow.
- Amino acids antagonize the effects of volume expansion on proximal sodium reabsorption, potentially via stimulation of sodium cotransport.
- Glomerular hyperfiltration during amino acid infusion may be explained by primary metabolic stimulation of proximal tubular function.