AJP - Gastrointestinal and Liver Physiology, Vol 267, Issue 2 308-G315, Copyright © 1994 by American Physiological Society
Apical-to-basolateral transepithelial transport of human lactoferrin in the intestinal cell line HT-29cl.19A
T. Mikogami, M. Heyman, G. Spik and J. F. Desjeux
Laboratoire de Chimie Biologique, Universite des Sciences et Technologies de Lille, France.
The role of human lactoferrin (hLf) in alimentary iron absorption across
intestinal cells was explored using a human differentiated colon carcinoma
cell line, HT-29cl.19A. The apical surface of HT-29cl.19A cell monolayers
exhibited 1.5 x 10(6) specific binding sites for hLf per cell, with a
dissociation constant of 8.3 x 10(-7) M. The apical-to-basolateral
transport of 125I-labeled hLf (125I-hLf) or 125I-59Fe-labeled hLf
(125I-[59Fe]hLf) was investigated using filter-grown HT-29cl.19A cell
monolayers mounted in Ussing chambers. Transport of total (intact plus
degraded) hLf, measured by the 125I flux, was not saturable up to an apical
hLf concentration of 12.5 microM, whereas immunoreactive hLf transport
measured by enzyme-linked immunoabsorbent assay was saturable at 3.75
microM. Lowering the temperature to 4 degrees C reduced the total and
immunoreactive hLf fluxes by 77% and 90%, and colchicine (500 microM)
reduced these fluxes by 30% and > 97%, respectively. These results
indicate that both types of transport are transcellular. Electrophoretic
analysis revealed that 125I-hLf transported to the basal compartment
consisted of largely degraded fragments (< 2 and 10-20 kDa) and a small
portion of intact hLf. At an apical concentration of 3.75 microM diferric
125I-[59Fe]hLf, the immunoreactive hLf flux (64.6 +/- 14.3 ng.h-1.cm-2)
constituted approximately 12% of the total hLf flux (552.0 +/- 61.6
ng.h-1.cm-2) and was similar to the [59Fe]hLf-equivalent flux (77.0 +/-
12.3 ng.h-1.cm-2).(ABSTRACT TRUNCATED AT 250 WORDS)
