Kidney Week

Abstract: TH-PO1101

Proximal Tubular Function Is Independent of Glomerular Filtration Rate

Session Information

• CKD: Mechanisms - 1
  October 24, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: CKD (Non-Dialysis)

• 2303 CKD (Non-Dialysis): Mechanisms

Authors

• Madero, Magdalena, Instituto Nacional de Cardiologia Ignacio Chavez, Ciudad de Mexico, Estado de Mexico, Mexico

Magdalena Madero, MD

• Fernandez Yepez, Ana K., Instituto Nacional de Cardiologia Ignacio Chavez, Ciudad de Mexico, Estado de Mexico, Mexico

Ana K. Fernandez Yepez, MD

• Montesinos Ojeda, Guadalupe Monserrat, Instituto Nacional de Cardiologia Ignacio Chavez, Ciudad de Mexico, Estado de Mexico, Mexico

Guadalupe Monserrat Montesinos Ojeda, MD

• Guzmán Portillo, Alan Jan, Instituto Nacional de Cardiologia Ignacio Chavez, Ciudad de Mexico, Estado de Mexico, Mexico

Alan Jan Guzmán Portillo, MD

• Estrada Escamilla, Aurora Itzel, Instituto Nacional de Cardiologia Ignacio Chavez, Ciudad de Mexico, Estado de Mexico, Mexico

Aurora Itzel Estrada Escamilla, MD

• Perez Allende Perez, Francisco, Instituto Nacional de Cardiologia Ignacio Chavez, Ciudad de Mexico, Estado de Mexico, Mexico

Francisco Perez Allende Perez, ScD

• Rodriguez-Iturbe, Bernardo, Instituto Nacional de Cardiologia Ignacio Chavez, Ciudad de Mexico, Estado de Mexico, Mexico

Bernardo Rodriguez-Iturbe, MD

Background

Tubular function is not routinely evaluated in kidney donors in the assumption that glomerular filtration rate (GFR) offers adequate representation of overall kidney health

Methods

We studied in kidney donors the response of cationic organic transporters (COT) with an oral dose of 5g of creatinine (cr) and anionic organic transporters (AOT) with an intravenous dose of 1mg/kg of furosemide (fr). Previous studies had shown that these doses resulted in maximal stimulation of CAT and AOT, respectively, without significant changes in GFR. Studies were done in 10 kidney donors (age 20-51 years; 3 females) before (2 kidneys or 2K) and 3 months after nephrectomy (1 kidney or 1K). GFR (iohexol), serum and urine cr (autoanalyzer) and urinary fr (HPLC) concentrations were determined in hourly blood and urine collections obtained 5 hours after the administration of cr and fr. Water diuresis was maintained during the studies and complete bladder emptying was determined by ultrasound. Tubular secretion of cr (TScr) was estimated as the subtraction of filtered creatinine (GFR x serum cr) from the urinary creatinine excretion (Ucr x Uvolume) and tubular secretion of furosemide (TSfr) = Ufr x Uvol. Data given are mean±95%CI

Results

First hour TScr and TSfr in the first hour (2K-TScr= 5.47±2.57 mg/min; 2K-TSfr= 0.39±0.123 mg/min) were 3-4 fold higher (p<0.01) than in subsequent hours when they remained essentially stable. The 1K responses were lower than the 2K responses, but also maximal in the first hour, (1K-TScr 3.38±0.981; 1K-TSfr 0.25±0.068) and stable afterwards. As There were no correlations between TScr or TSfr with the GFR in 2K or 1K studies (Figure 1) and no consistent changes between 2K and 1K studies in the relation between GFR and TScr or TSfr

Conclusion

The data show that stimulated functional responses of OCT and OAT in kidney donors, neither pre nor post-nephrectomy, are related to GFR and deserve evaluation of their prognostic relevance.