UT-A2: a 55-kDa urea transporter in thin descending limb whose abundance is regulated by vasopressin.
The renal urea transporter gene (UT-A) produces different transcripts in the inner medullary collecting ducts (UT-A1) and thin descending limbs of Henle's loop (UT-A2), coding for distinct proteins. Peptide-directed rabbit polyclonal antibodies were used to identify the UT-A2 protein in renal medulla of mouse and rat. In the inner stripe of outer medulla, an antibody directed to the COOH terminus of UT-A recognized a membrane protein of 55 kDa. The abundance of this 55-kDa protein was strongly increased in response to chronic infusion of the vasopressin analog 1-deamino-[8-D-arginine]vasopressin (DDAVP) in Brattleboro rats, consistent with previous evidence that UT-A2 mRNA abundance is markedly increased. Immunofluorescence labeling with the COOH-terminal antibody in Brattleboro rats revealed labeling in the lower portion of descending limbs from short-looped nephrons (in the aquaporin-1-negative portion of this segment). This UT-A labeling was increased in response to DDAVP. Increased labeling was also seen in descending limbs of long-looped nephrons in the base of the inner medulla. These results indicate that UT-A2 is expressed as a 55-kDa protein in portions of the thin descending limbs of Henle's loop and that the abundance of this protein is strongly upregulated by vasopressin.
Wade
J B
JB
Department of Physiology, Univ. of Maryland School of Medicine, Baltimore, MD 21201, USA.
Lee
A J
AJ
Liu
J
J
Ecelbarger
C A
CA
Mitchell
C
C
Bradford
A D
AD
Terris
J
J
Kim
G H
GH
Knepper
M A
MA
D000818:Animals; D000906:Antibodies / Q000276:immunology; D051398:Aquaporin 1; D020346:Aquaporins / Q000378:metabolism; D002352:Carrier Proteins / Q000276:immunology / Q000378:metabolism*; D003894:Deamino Arginine Vasopressin / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D015151:Immunoblotting; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D008562:Membrane Glycoproteins / Q000276:immunology / Q000378:metabolism*; D026901:Membrane Transport Proteins; D051379:Mice; D008807:Mice, Inbred BALB C; D020033:Protein Isoforms / Q000276:immunology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015854:Up-Regulation; D014667:Vasopressins / Q000502:physiology*; D000096982:Urea Transporters
D000906:Antibodies; D051398:Aquaporin 1; D020346:Aquaporins; D002352:Carrier Proteins; D003894:Deamino Arginine Vasopressin; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D020033:Protein Isoforms; D014667:Vasopressins; D000096982:Urea Transporters; C496021:Aqp1 protein, mouse; C496022:Aqp1 protein, rat