A method to evaluate renal ammoniagenesis in vivo

Area of Science:

• Nephrology
• Physiology
• Biochemistry

Background:

• Reduced ammonium (NH4+) excretion can stem from low production or impaired transfer to urine.
• Current methods for measuring in vivo NH4+ production are invasive.
• A non-invasive method is needed to assess kidney NH4+ production.

Purpose of the Study:

• To develop a non-invasive test to measure the in vivo rate of ammonium (NH4+) production in the kidney.
• To identify conditions that maximize NH4+ transfer to urine for measurement.

Main Methods:

• Initial studies in dogs to correlate NH4+ production and excretion.
• Administering furosemide (loop diuretic) and fludrocortisone in humans to induce low urine pH and high flow rate.
• Measuring urine pH, flow rate, and NH4+ excretion rates.

Main Results:

• In dogs, NH4+ excretion varied widely and wasn't directly linked to production.
• NH4+ excretion increased significantly when urine pH was < 6 or urine flow was high.
• In humans, furosemide and fludrocortisone lowered urine pH to 5.1 and increased flow to 8 ml/min.
• NH4+ excretion in humans rose from 21 to 33 mumol/min with increased urine flow.

Conclusions:

• Manipulating urine pH and flow rate can enhance ammonium (NH4+) excretion.
• This approach shows promise for a non-invasive method to estimate in vivo NH4+ production.
• Further research is needed to validate this non-invasive technique in clinical settings.