HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Supplemental Videos All Versions of this Article: 287/2/C517    most recent 00006.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (25) Citing Articles via Google Scholar Google Scholar Articles by Sandoval, R. M. Articles by Molitoris, B. A. Search for Related Content PubMed PubMed Citation Articles by Sandoval, R. M. Articles by Molitoris, B. A.

PROTEIN AND VESICLE TRAFFICKING, CYTOSKELETON

Uptake and trafficking of fluorescent conjugates of folic acid in intact kidney determined using intravital two-photon microscopy

¹Division of Nephrology, Department of Medicine, Indiana University School of Medicine, and The Indiana Center for Biological Microscopy, Indianapolis; ³Department of Chemistry, Purdue University, West Lafayette, Indiana 47907; and ²The Roudebush Veterans Affairs Medical Center, Indianapolis 46202

Submitted 6 January 2004 ; accepted in final form 1 April 2004

Intravital two-photon microscopy was used to follow the uptake and trafficking of fluorescent conjugates of folic acid in the rat kidney. Intravenously administered folate-linked dye molecules quickly filled the plasma volume but not cellular components of the blood. Glomerular filtration occurred immediately and binding to proximal tubule cells was seen within seconds. Fluorescence from a pH-insensitive conjugate of folic acid, folate Texas red (FTR), was readily observed on the apical surface of the proximal tubules and in multiple cellular compartments, but little binding or uptake could be detected in any other kidney cells. Fluorescence from a pH-sensitive conjugate of folic acid, folate fluorescein, was seen only on the apical surface of proximal tubule cells, suggesting that internalized folate conjugates are localized to acidic compartments. The majority of the FTR conjugate internalized by proximal tubules accumulated within a lysosomal pool, as determined by colocalization studies. However, portions of FTR were also shown by electron microscopy to undergo transcytosis from apical to basal domains. Additional studies with colchicine, which is known to depolymerize microtubules and interrupt transcytosis, produced a marked reduction in endocytosis of FTR, with accumulation limited to the subapical region of the cell. No evidence of cytosolic release of either folate conjugate was observed, which may represent a key difference from the cytosolic deposition seen in neoplastic cells. Together, these data support the argument that folate conjugates (and, by extrapolation, physiological folate) bind to the apical surface of proximal tubule cells and are transported into and across the cells in endocytic compartments.

proximal tubule cell

This article has been cited by other articles:

				C. Muller, F. Forrer, R. Schibli, E. P. Krenning, and M. de Jong SPECT Study of Folate Receptor-Positive Malignant and Normal Tissues in Mice Using a Novel 99mTc-Radiofolate J. Nucl. Med., February 1, 2008; 49(2): 310 - 317. [Abstract] [Full Text] [PDF]

				W. Yu, R. M. Sandoval, and B. A. Molitoris Rapid determination of renal filtration function using an optical ratiometric imaging approach Am J Physiol Renal Physiol, June 1, 2007; 292(6): F1873 - F1880. [Abstract] [Full Text] [PDF]

				C. Muller, M. Bruhlmeier, P. A. Schubiger, and R. Schibli Effects of Antifolate Drugs on the Cellular Uptake of Radiofolates In Vitro and In Vivo J. Nucl. Med., December 1, 2006; 47(12): 2057 - 2064. [Abstract] [Full Text] [PDF]

				J. J. Kang, I. Toma, A. Sipos, F. McCulloch, and J. Peti-Peterdi Quantitative imaging of basic functions in renal (patho)physiology Am J Physiol Renal Physiol, August 1, 2006; 291(2): F495 - F502. [Abstract] [Full Text] [PDF]

				H. Birn The kidney in vitamin B12 and folate homeostasis: characterization of receptors for tubular uptake of vitamins and carrier proteins Am J Physiol Renal Physiol, July 1, 2006; 291(1): F22 - F36. [Abstract] [Full Text] [PDF]

				W. Yu, R. M. Sandoval, and B. A. Molitoris Quantitative intravital microscopy using a Generalized Polarity concept for kidney studies Am J Physiol Cell Physiol, November 1, 2005; 289(5): C1197 - C1208. [Abstract] [Full Text] [PDF]

				G. A. Tanner, R. M. Sandoval, B. A. Molitoris, J. R. Bamburg, and S. L. Ashworth Micropuncture gene delivery and intravital two-photon visualization of protein expression in rat kidney Am J Physiol Renal Physiol, September 1, 2005; 289(3): F638 - F643. [Abstract] [Full Text] [PDF]

				B. A. Molitoris and R. M. Sandoval Intravital multiphoton microscopy of dynamic renal processes Am J Physiol Renal Physiol, June 1, 2005; 288(6): F1084 - F1089. [Abstract] [Full Text] [PDF]

				S. X. Lin and F. R. Maxfield Fluorescence imaging in living animals. Focus on "Uptake and trafficking of fluorescent conjugates of folic acid in intact kidney determined using intravital two-photon microscopy" Am J Physiol Cell Physiol, August 1, 2004; 287(2): C257 - C259. [Full Text] [PDF]