A New Method for Estimating Glomerular Filtration Rate in Rhesus Macaques (Macaca mulatta)

Area of Science:

• Nephrology
• Radiology
• Comparative Medicine

Background:

• Late effects of irradiation include chronic kidney injury (CKI), impacting morbidity and mortality.
• Glomerular filtration rate (GFR) is the key indicator of kidney function, but traditional markers may not detect early damage.
• Current GFR measurement methods are complex and costly, necessitating simpler alternatives.

Purpose of the Study:

• To evaluate the applicability of the Schwartz formula, commonly used in human pediatrics, for estimating GFR in rhesus macaques.
• To determine if the Schwartz formula-estimated GFR (eGFR) correlates with iohexol-measured GFR in irradiated and non-irradiated macaques.

Main Methods:

• Iohexol clearance was measured in 12 rhesus macaques with varying blood urea nitrogen (BUN) levels and 4 controls.
• GFR was calculated using plasma iohexol concentrations determined by mass spectrometry post-injection.
• The Schwartz formula was used to calculate eGFR for comparison with iohexol-GFR.

Main Results:

• A significant positive correlation was observed between iohexol-GFR and Schwartz formula-eGFR.
• In macaques receiving <6 Gy irradiation, males exhibited higher GFR than females.
• Macaques with renal irradiation doses >6 Gy showed lower GFR compared to those with <6 Gy doses.

Conclusions:

• The Schwartz formula provides a rapid, non-invasive, and cost-effective estimation of GFR in rhesus macaques.
• This method can aid in the clinical assessment of renal function and kidney injury in irradiated macaques.
• The study validates a simpler approach to GFR estimation in a non-human primate model.