title: Expression of urea transporters in the developing rat kidney.
abstract: Urea transport in the kidney is mediated by a family of transporter proteins that includes renal urea transporters (UT-A) and erythrocyte urea transporters (UT-B). Because newborn rats are not capable of producing concentrated urine, we examined the time of expression and the distribution of UT-A and UT-B in the developing rat kidney by light and electron microscopic immunocytochemistry. Kidneys from 16-, 18-, and 20-day-old fetuses, 1-, 4-, 7-, 14-, and 21-day-old pups, and adult animals were studied. In the adult kidney, UT-A was expressed intensely in the inner medullary collecting duct (IMCD) and terminal portion of the short-loop descending thin limb (DTL) and weakly in long-loop DTL in the outer part of the inner medulla. UT-A immunoreactivity was not present in the fetal kidney but was observed in the IMCD and DTL in 1-day-old pups. The intensity of UT-A immunostaining in the IMCD gradually increased during postnatal development. In 4- and 7-day-old pups, UT-A immunoreactivity was present in the DTL at the border between the outer and inner medulla. In 14- and 21-day-old pups, strong UT-A immunostaining was observed in the terminal part of short-loop DTL in the outer medulla, and weak labeling remained in long-loop DTL descending into the outer part of the inner medulla. In the adult kidney, there was intense staining for UT-B in descending vasa recta (DVR) and weak labeling of glomeruli. In the developing kidney, UT-B was first observed in the DVR of a 20-day-old fetus. After birth there was a striking increase in the number of UT-B-positive DVR, in association with the formation of vascular bundles. The intensity of immunostaining remained strong in the outer medulla but gradually decreased in the inner medulla. We conclude that the expression of urea transporters in short-loop DTL and DVR coincides with the development of the ability to produce a concentrated urine.
authors.affiliation: Department of Anatomy, Catholic University Medical College, Seoul, Korea, 137-701, Georgia 30322, USA.
authors.forename: Young-Hee
authors.initials: YH
authors.lastname: Kim
authors.forename: Dong-Un
authors.initials: DU
authors.lastname: Kim
authors.forename: Ki-Hwan
authors.initials: KH
authors.lastname: Han
authors.forename: Ju-Young
authors.initials: JY
authors.lastname: Jung
authors.forename: Jeff M
authors.initials: JM
authors.lastname: Sands
authors.forename: Mark A
authors.initials: MA
authors.lastname: Knepper
authors.forename: Kirsten M
authors.initials: KM
authors.lastname: Madsen
authors.forename: Jin
authors.initials: J
authors.lastname: Kim
mesh_terms: D000367:Age Factors; D000818:Animals; D000918:Antibody Specificity; D002352:Carrier Proteins / Q000032:analysis* / Q000276:immunology; D007124:Immunoenzyme Techniques; D007671:Kidney Concentrating Ability / Q000502:physiology; D008138:Loop of Henle / Q000737:chemistry* / Q000196:embryology* / Q000648:ultrastructure; D008562:Membrane Glycoproteins / Q000032:analysis* / Q000276:immunology; D026901:Membrane Transport Proteins; D016253:Microscopy, Immunoelectron; D051381:Rats; D017207:Rats, Sprague-Dawley; D000096982:Urea Transporters
chemical_list: D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D000096982:Urea Transporters