Ultrastructural localization of UT-A and UT-B in rat kidneys with different hydration status.
Urea transport in the kidney is mediated by a family of transporter proteins, including renal urea transporters (UT-A) and erythrocyte urea transporters (UT-B). We aimed to determine whether hydration status affects the subcellular distribution of urea transporters. Male Sprague-Dawley rats were divided into three groups: dehydrated rats (WD) given minimum water, hydrated rats (WL) given 3% sucrose in water for 3 days before death, and control rats given free access to water. We labeled kidney sections with antibodies against UT-A1 and UT-A2 (L194), UT-A3 (Q2), and UT-B using preembedding immunoperoxidase and immunogold methods. In control animals, UT-A1 and UT-A3 immunoreactivities were observed throughout the cytoplasm in inner medullary collecting duct (IMCD) cells, and weak labeling was observed on the basolateral plasma membrane. UT-A2 immunoreactivity in the descending thin limbs (DTL) was observed mainly on the apical and basolateral membranes of type I epithelium, and very faint labeling was observed in the long-loop DTL at the border between the outer and inner medulla. UT-A1 immunoreactivity intensity was markedly lower, and UT-A3 immunoreactivity was higher in IMCD of WD vs. controls. UT-A2 immunoreactivity intensities in the plasma membrane and cytoplasm of type I, II, and III epithelia of DTL were greater in WD vs. controls. In contrast, UT-A1 expression was greater and UT-A2 and UT-A3 expressions were lower in WL vs. controls. The subcellular distribution of UT-A in DTL or IMCD did not differ between control and experimental animals. UT-B was expressed in the plasma membrane of the descending vasa recta of both control and experimental animals. UT-B intensity was higher in WD and lower in WL vs. controls. These data indicate that changes in hydration status over 3 days affected urea transporter protein expression without changing its subcellular distribution.
Lim
Sun-Woo
SW
Department of Anatomy, The Catholic University of Korea, Seoul, Korea.
Han
Ki-Hwan
KH
Jung
Ju-Young
JY
Kim
Wan-Young
WY
Yang
Chul-Woo
CW
Sands
Jeff M
JM
Knepper
Mark A
MA
Madsen
Kirsten M
KM
Kim
Jin
J
D000818:Animals; D001834:Body Water / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism* / Q000648:ultrastructure*; D008297:Male; D026901:Membrane Transport Proteins / Q000378:metabolism*; D021381:Protein Transport; D051381:Rats; D017207:Rats, Sprague-Dawley; D000096982:Urea Transporters
D026901:Membrane Transport Proteins; D000096982:Urea Transporters