Wagner, C A; Waldegger, S; Osswald, H; Biber, J; Murer, H; Busch, A E; Lang, F (1996). Heavy metals inhibit Pi-induced currents through human brush-border NaPi-3 cotransporter in Xenopus oocytes. American Journal of Physiology: Renal Physiology, 271(4 Pt 2):F926-F930.
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Heavy metal intoxication with Hg2+, Pb2+ and Cd2+ commonly leads to phosphaturia. In this study, we examined the effects of these heavy metals on Pi-induced currents (Ip) through NaPi-3, the human renal cotransporter for Na+ and Pi. Hg2+ inhibited Ip in a dose- and time-dependent fashion. Hg2+ decreased the extrapolated maximal current but did not alter the apparent affinity for Pi. This inhibition was also observed with the membrane-permeable oxidizing agent 2,2'-dithio-bis(5-nitropyridine) (DTNP) but not with the membrane-impermeable 5,5'-dithiobis(2-nitrobenzoic acid). Hg(2+)- and DTNP-mediated inhibition of Ip was reversible only in the presence of the reducing agent 2,3-dihydroxybutane-1,4-dithiol. Cd2+ and Pb2+ also inhibited Ip. However, while CD2+ did not significantly alter the apparent affinity for Pi, the apparent concentration needed for half-maximal current (Km) for Pi was increased by Pb2+. In contrast to Hg2+, the inhibition of Ip by Cd2+ and Pb2+ was rapidly reversible upon washout. In the presence of the Na(+)-K(+)-adenosinetriphosphatase inhibitor ouabain, Ip was not reduced, and the effects of the heavy metals were maintained. In summary, the three heavy metals Hg2+, Cd2+, and Pb2+ inhibit Ip through the Na+/Pi cotransporter NaPi-3 by distinct mechanisms. Heavy metal-mediated inhibition of NaPi-3 may be responsible for the phosphaturia observed after intoxication with these compounds.
|Item Type:||Journal Article, refereed|
|Communities & Collections:||04 Faculty of Medicine > Institute of Physiology
07 Faculty of Science > Institute of Physiology
|Dewey Decimal Classification:||570 Life sciences; biology|
|Date:||1 October 1996|
|Deposited On:||11 Feb 2008 12:22|
|Last Modified:||27 Nov 2013 19:37|
|Publisher:||American Physiological Society|
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