UT-A expression in pars recta from a rat model of chronic renal failure.
BACKGROUND
Urea transport depends on the diffusion through 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 involved in intrarenal recycling of urea. The aim of our study was to examine the renal urea handling in rats with chronic renal failure (CRF).


METHODS
CRF rats were induced by 5/6 nephrectomy followed by a high-protein (HP) diet to increase the progressive loss of renal function for 5 months. Functional studies on water and urea handling were performed. RT-PCR, immunoblotting and immunohistochemistry were used to identify UT-A proteins in remnant kidney.


RESULTS
A significant decrease in creatinine clearance consistent with development of CRF was observed. The remnant kidneys were hypertrophied, and total renal mass was increased. Urine production increased markedly, whereas urine osmolality and solute-free water reabsorption decreased significantly. Fractional urea excretion was increased reaching values of 105% -/+ 8%. UT-A protein was localized in pars recta by immunohistochemical studies, and it was identified as UT-A2 in outer medulla from remnant kidneys by RT-PCR and immunoblotting.


CONCLUSIONS
In uremic rats, an urea transporter type UT-A2 was expressed in the pars recta, suggesting a possible relation with the fractional urea excretion increase. This expression may be a consequence of an adaptive mechanism in the handling of urea during development of CRF. Further studies will be necessary to elucidate the contribution of this mechanism to renal damage observed in the progression of CRF.
Zotta
Elsa
E
Physiopathogeny Laboratory, Department of Physiology, Faculty of Medicine, University of Buenos Aires, Buenos Aires - Argentina. ezotta@fmed.uba.ar
Ochoa
Federico
F
Tironi Farinati
Carla
C
Damiano
Alicia
A
Silberstein
Claudia
C
Levy Yeyati
Nesmo
N
Ibarra
Cristina
C
D000818:Animals; D004195:Disease Models, Animal; D005500:Follow-Up Studies; D015870:Gene Expression; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D007667:Kidd Blood-Group System; D007676:Kidney Failure, Chronic / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D007679:Kidney Medulla / Q000378:metabolism* / Q000473:pathology; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000096982:Urea Transporters
D007667:Kidd Blood-Group System; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; D000096982:Urea Transporters