UT-A expression in pars recta from a rat model of chronic renal failure

ZOTTA ELSA; OCHOA FEDERICO; TIRONI FARINATI CARLA; DAMIANO ALICIA; SILBERSTEIN CLAUDIA; LEVY YEYATI NESMO; IBARRA CRISTINA

JOURNAL OF NEPHROLOGY.

Wichtig Editore

Año: 2008 vol. 21 p. 948 - 959

1120-3625

ABSTRACTBackground: Urea transport depends on the diffusionthrough cell membrane and the facilitated urea transport.Two groups of urea transporters (UT-A and UT-B)have been identified in mammals, and both are involvedin intrarenal recycling of urea. The aim of our study wasto examine the renal urea handling in rats with chronicrenal failure (CRF).Methods: CRF rats were induced by 5/6 nephrectomy followedby a high-protein (HP) diet to increase the progressiveloss of renal function for 5 months. Functionalstudies on water and urea handling were performed. RTPCR,immunoblotting and immunohistochemistry wereused to identify UT-A proteins in remnant kidney.Results: A significant decrease in creatinine clearanceconsistent with development of CRF was observed. Theremnant kidneys were hypertrophied, and total renalmass was increased. Urine production increasedmarkedly, whereas urine osmolality and solute-free waterreabsorption decreased significantly. Fractional ureaexcretion was increased reaching values of 105% ± 8%.UT-A protein was localized in pars recta by immunohistochemicalstudies, and it was identified as UT-A2 in outermedulla from remnant kidneys by RT-PCR and immunoblotting.Conclusion: In uremic rats, an urea transporter type UT-A2was expressed in the pars recta, suggesting a possiblerelation with the fractional urea excretion increase. Thisexpression may be a consequence of an adaptive mechanismin the handling of urea during development of CRF.Further studies will be necessary to elucidate the contributionof this mechanism to renal damage observed inthe progression of CRF.