title: Galectin-3 expression is induced in renal beta-intercalated cells during metabolic acidosis.
abstract: The adaptation of the cortical collecting duct (CCD) to metabolic acidosis requires the polymerization and deposition in the extracellular matrix of the novel protein hensin. HCO3(-)-secreting beta-intercalated cells remove apical Cl-:HCO3(-) exchangers and may reverse functional polarity to secrete protons. Using intercalated cells in culture, we found that galectin-3 facilitated hensin polymerization, thereby causing their differentiation into the H+-secreting cell phenotype. We examined the expression of galectin-3 in the rabbit kidney and its relationship to hensin during metabolic acidosis. In control kidneys, galectin-3 was expressed in the cortical and medullary collecting ducts. In the outer cortex 26 +/- 3% of CCD cells expressed galectin-3 compared with 64 +/- 3% of the cells of the inner cortex. In the CCD, galectin-3 was rarely expressed in beta-intercalated cells, being primarily present in alpha-intercalated and principal cells. During metabolic acidosis, the intensity of cellular staining for galectin-3 increased and more cells began to express it; the percentage of CCD cells expressing galectin-3 increased from 26 +/- 3 to 66 +/- 3% in the outer cortex and from 64 +/- 3 to 78 +/- 4% in the inner cortex. This was particularly evident in beta-intercalated cells where expression was found in only 8 +/- 2% in control animals but in 75 +/- 2% during metabolic acidosis in the outer cortex and similarly for the inner cortex (26 +/- 6 to 90 +/- 7%). Importantly, both galectin-3 and hensin were found in the extracellular matrix of microdissected CCDs; and during metabolic acidosis, many more cells exhibited this extracellular colocalization. Thus galectin-3 may play several important roles in the CCD, including mediating the adaptation of beta-intercalated cells during metabolic acidosis.
authors.affiliation: Department of Pediatrics, University of Rochester School of Medicine, New York, USA.
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Schwaderer
authors.forename: Soundarapandian
authors.initials: S
authors.lastname: Vijayakumar
authors.forename: Qais
authors.initials: Q
authors.lastname: Al-Awqati
authors.forename: George J
authors.initials: GJ
authors.lastname: Schwartz
mesh_terms: D000138:Acidosis / Q000378:metabolism*; D000818:Animals; D016326:Extracellular Matrix Proteins / Q000378:metabolism* / Q000648:ultrastructure; D037502:Galectin 3 / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D007150:Immunohistochemistry; D007668:Kidney / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D018613:Microscopy, Confocal; D011817:Rabbits; D051381:Rats; D051116:Receptors, Scavenger / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D016326:Extracellular Matrix Proteins; D037502:Galectin 3; D051116:Receptors, Scavenger; C495130:hensin protein, rabbit