title: Modulation of the mdr-1b gene in the kidney of rats subjected to dehydration or a high-salt diet.
abstract: The localization of the multidrug resistance gene (mdr-1b) messenger ribonucleic acid (mRNA) along the rat nephron and its regulation was investigated under two different experimental situations: dehydration and high-Na+ diet. The mdr-1b mRNA was detected in glomeruli, proximal tubule segments, cortical and medullary thick ascending limbs, inner medullary collecting ducts and thin limbs of Henle's loop. Using the ribonuclease (RNase) protection assay (RPA), the abundance of mdr-1b mRNA was shown to be 35% less in renal cortex than in medulla. The mdr-1b mRNA expression in dehydrated rats in cortex or medulla did not differ from control. However, after 5 or 14 days on a high-Na+ diet, mdr-1b expression had decreased significantly in both cortex and medulla. There was no change in protein expression in dehydrated rats but a significant decrease occurred in rats fed the high-salt diet, confirming the results obtained with RPA. Our results suggest that the mdr-1b product is involved in extracellular volume regulation in rats.
authors.affiliation: Instituto de Biofísica, Carlos Chagas Filho-Universidade Federal do Rio de Janeiro, RJ, Brazil.
authors.forename: M M
authors.initials: MM
authors.lastname: Morales
authors.forename: M A
authors.initials: MA
authors.lastname: Capella
authors.forename: M V
authors.initials: MV
authors.lastname: Sanches
authors.forename: A G
authors.initials: AG
authors.lastname: Lopes
authors.forename: W B
authors.initials: WB
authors.lastname: Guggino
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics*; D000315:Adrenalectomy; D000450:Aldosterone / Q000494:pharmacology; D000818:Animals; D015139:Blotting, Southern; D015153:Blotting, Western; D003681:Dehydration / Q000378:metabolism*; D004032:Diet; D004573:Electrolytes / Q000378:metabolism; D005919:Glomerular Filtration Rate / Q000187:drug effects / Q000502:physiology; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009399:Nephrons / Q000187:drug effects / Q000378:metabolism; D009994:Osmolar Concentration; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012260:Ribonucleases / Q000378:metabolism; D012982:Sodium, Dietary / Q000494:pharmacology*; D013997:Time Factors; D000097202:ATP-Binding Cassette Sub-Family B Member 4
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D000450:Aldosterone; D004573:Electrolytes; D012333:RNA, Messenger; D012260:Ribonucleases; D012982:Sodium, Dietary; D000097202:ATP-Binding Cassette Sub-Family B Member 4