Mechanisms of zinc uptake in gills of freshwater rainbow trout:
interplay with calcium transport.
Hogstrand, Christer, Pieter M. Verbost, Sjoerd E. Wendelaar Bonga, and
Chris M. Wood.
T.H. Morgan School of Biological Sciences, 101 Morgan Building,
University of Kentucky, Lexington, Kentucky 40506-0225, U.S.A.,
Katholieke Universiteit Nijmegen, Faculteit der Natuurwetenschappen,
Postbus 9010, 6500 GL Nijmegen, The Netherlands, Master University,
Department of Biology, 1280 Main Street West, Hamilton L8S 4K1,
Ontario, Canada
APStracts 2:0327R, 1995.
The uptake mechanism of Zn2+ through the gill epithelium of freshwater
rainbow trout was investigated both in intact animals and in isolated
basolateral membranes. Involvement of the apical Ca2+ uptake sites in
Zn2+ uptake was examined in vivo by pharmacological manipulation of
the apical Ca2+ permeability. The apical entries of Ca2+ and Zn2+,
but not Na+ and Cl-, were inhibited by addition of La to the water.
Addition of 1.0 [mu]M La reduced the influxes of Ca2+ and Zn2+ to
22+/-3% and 53+/-7% (mean+/-SEM) of the control value, respectively.
Injection of CaCl2 also reduced the branchial influxes of Ca2+ and
Zn2+. This treatment decreased the influx of Ca2+ to 45+/-4% of the
control level and the Zn2+ influx to 68+/-5%. These results strongly
imply that Zn2+ passes across the apical membrane of the chloride
cells of the gills via the same pathway as Ca2+. The presence of an
active basolateral transporter for Zn2+ was investigated in vitro on
isolated basolateral membranes. There was no ATP-dependent or Na+
-gradient driven transport of Zn2+ at physiological Zn2+ activities.
The same system was used to study potential effects of Zn2+ on the
basolateral Ca2+-ATPase. Zn2+ was found to be a potent blocker of
this transporter, causing a mixed inhibitory effect on the ATP-driven
Ca transport at a free Zn2+ activity of 100 pM.
Received 3 April 1995; accepted in final form 15 November 1995.
APS Manuscript Number R218-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95