Dietary sulfate regulates the expression of the renal brush border Na/Si cotransporter NaSi-1.
Dietary inorganic sulfate (Si) intake is an important factor in the regulation of renal proximal tubular sodium-dependent Si transport (Na/Si cotransport). The purpose of the present study was to determine whether modulation of Na/Si cotransport activity by dietary Si is mediated through regulation of the renal expression of the recently cloned NaSi-1 protein located in the apical brush border membrane (BBM) of the proximal tubule. It was found that rats fed a high Si diet had a marked increase in the renal excretion of Si and a concomitant decrease in BBM Na/Si cotransport activity when compared with rats on a control Si diet. The 43% decrease in BBM Na/Si cotransport activity was associated with a 33% decrease in BBM NaSi-1 protein abundance, as determined by Western blotting, and a 2.7-fold decrease in cortical NaSi-1 mRNA abundance, as determined by Northern blotting. Furthermore, cortical mRNA from rats fed a high Si diet when injected into Xenopus laevis oocytes led to a 2.2-fold decrease in Na/Si cotransport activity compared with mRNA isolated from control Si diet rats. This study indicates that adaptation to a high Si diet is accompanied by a decrease in renal cortical NaSi-1 mRNA abundance, which results in reduced expression of the NaSi-1 protein at the level of the proximal tubular BBM.
Markovich
D
D
Department of Physiology and Pharmacology, University of Queensland, Brisbane, Australia.
Murer
H
H
Biber
J
J
Sakhaee
K
K
Pak
C
C
Levi
M
M
D000222:Adaptation, Physiological / Q000187:drug effects; D000818:Animals; D001692:Biological Transport; D015152:Blotting, Northern; D015153:Blotting, Western; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism*; D027682:Cation Transport Proteins; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D019587:Dietary Supplements; D004195:Disease Models, Animal; D066298:In Vitro Techniques; D008297:Male; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D012333:RNA, Messenger / Q000008:administration & dosage / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D000077003:Sodium Sulfate Cotransporter; D013431:Sulfates / Q000008:administration & dosage / Q000378:metabolism*; D027981:Symporters; D014982:Xenopus laevis
D002352:Carrier Proteins; D027682:Cation Transport Proteins; D012333:RNA, Messenger; D000077003:Sodium Sulfate Cotransporter; D013431:Sulfates; D027981:Symporters