TY - JOUR
T1 - Intestinal zinc uptake in freshwater rainbow trout
T2 - Evidence for apical pathways associated with potassium efflux and modified by calcium
AU - Glover, Chris N.
AU - Bury, Nicolas R.
AU - Hogstrand, Christer
N1 - Funding Information:
The research described herein was supported by United States Environmental Protection Agency Grant (R826104) awarded to CH, while CG was funded in part by the Society of Environmental Toxicology and Chemistry (SETAC) Doctoral Fellowship in Environmental Science, sponsored by Proctor & Gamble Company. Animal care and handling was performed in accordance with, and with approval given under, the Animal (Scientific Procedures) Act (UK) 1986.
PY - 2004/5/27
Y1 - 2004/5/27
N2 - Understanding the mechanisms of intestinal zinc uptake in fish is of considerable interest from both nutritional and toxicological perspectives. In this study, properties of zinc transport across the apical membrane of freshwater rainbow trout intestinal epithelia were examined using right-side-out brush border membrane vesicles (BBMV's). Extravesicular calcium was found to have complex actions on zinc uptake. At a low zinc concentration of 1 μM, calcium (0.1-2 mM) significantly stimulated zinc uptake. In contrast, calcium inhibited zinc uptake at higher zinc levels (100 μM). Lanthanum and cadmium in the external medium did not block zinc uptake, suggesting that interactions between zinc and calcium were not exerted at a calcium channel. Copper also failed to exercise any inhibitory action. Zinc association with the BBMV's was enhanced by an outward potassium gradient. This stimulatory effect was only present at a zinc concentration of 100 μM. The potassium channel blocker, tetraethylammonium chloride inhibited zinc uptake at this relatively high zinc concentration, suggesting the presence of a low affinity zinc uptake pathway linked to potassium efflux. The present study provides evidence that the mechanism of intestinal zinc uptake in rainbow trout is pharmacologically very different from that of the piscine gill and the mammalian intestine.
AB - Understanding the mechanisms of intestinal zinc uptake in fish is of considerable interest from both nutritional and toxicological perspectives. In this study, properties of zinc transport across the apical membrane of freshwater rainbow trout intestinal epithelia were examined using right-side-out brush border membrane vesicles (BBMV's). Extravesicular calcium was found to have complex actions on zinc uptake. At a low zinc concentration of 1 μM, calcium (0.1-2 mM) significantly stimulated zinc uptake. In contrast, calcium inhibited zinc uptake at higher zinc levels (100 μM). Lanthanum and cadmium in the external medium did not block zinc uptake, suggesting that interactions between zinc and calcium were not exerted at a calcium channel. Copper also failed to exercise any inhibitory action. Zinc association with the BBMV's was enhanced by an outward potassium gradient. This stimulatory effect was only present at a zinc concentration of 100 μM. The potassium channel blocker, tetraethylammonium chloride inhibited zinc uptake at this relatively high zinc concentration, suggesting the presence of a low affinity zinc uptake pathway linked to potassium efflux. The present study provides evidence that the mechanism of intestinal zinc uptake in rainbow trout is pharmacologically very different from that of the piscine gill and the mammalian intestine.
KW - Calcium
KW - Dietary metal
KW - Fish
KW - Intestine
KW - Potassium channel
KW - Zinc
UR - http://www.scopus.com/inward/record.url?scp=2442442430&partnerID=8YFLogxK
U2 - 10.1016/j.bbamem.2004.03.008
DO - 10.1016/j.bbamem.2004.03.008
M3 - Journal Article
C2 - 15157623
AN - SCOPUS:2442442430
SN - 0005-2736
VL - 1663
SP - 214
EP - 221
JO - Biochimica et Biophysica Acta - Biomembranes
JF - Biochimica et Biophysica Acta - Biomembranes
IS - 1-2
ER -