Evaluation of glomerular filtration rate is very important in both preclinical and clinical setting, especially in the context of chronic kidney disease. It is typically performed using ⁵¹ Cr-EDTA or by imaging with ¹²³ I-Hippuran scintigraphy, which has a significantly lower resolution and sensitivity as compared to PET. ⁶⁸ Ga-EDTA represents a valid alternative due to its quick availability using a ⁶⁸ Ge/ ⁶⁸ Ga generator, while PET/CT enables both imaging of renal function and accurate quantitation of clearance of activity from both plasma and urine. Therefore, we aimed at investigating the use of ⁶⁸ Ga-EDTA as a preclinical tracer for determining renal function in a knock-in rat model known to present progressive decline of renal function.
⁶⁸ Ga-EDTA was injected in 23 rats, either wild type (n=10) or knock-in (n=13). By applying a unidirectional, two-compartment model and Rutland-Patlak Plot linear regression analysis, split renal function was determined from the age of 6 weeks to 12 months.
Glomerular filtration ranged from 0.025±0.01 ml/min at 6 weeks to 0.049±0.05 ml/min at 6 months in wild type rats. Glomerular filtration was significantly lower in knock-in rats at 6 and 12 months (P<0.01). No significant difference was observed in renal volumes between knock-in and wild type animals, based on imaging-derived volume calculations.
⁶⁸ Ga-EDTA turned out to be a very promising PET/CT tracer for the evaluation of split renal function. This method allowed detection of progressive renal impairment in a knock-in rat model. Additional validation in a human cohort is warranted to further assess clinical utility in both, healthy individuals and patients with renal impairment.