TRANSPORT OF SELENATE AND SULPHATE ACROSS THE INTESTINAL BRUSH-BORDER MEMBRANE OF PIG JEJUNUM BY TWO COMMON MECHANISMS

¹ Institut für Veterinär-Physiologie, Universität Züurich, Winterthurerstrasse 260, CH-8057 Zürich, Switzerland

The objectives of the present study were to find out whether selenate and sulphate are transported by a common Na⁺-dependent transport mechanism across the intestinal brush-border membrane and whether selenate is also transported by the anion-exchange system transporting sulphate across the brush-border membrane. Results from cis-inhibition as well as from trans-stimulation experiments show that selenate and sulphate are transported across the brush-border membrane by both Na⁺ co-transport and anion exchange. The influence of various dicarboxylates (oxalate, oxaloacetate, glutamate) and of the anion-exchange inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulphonate (DIDS) on selenate and sulphate transport across the brush-border membrane was also investigated. Under Na⁺-gradient conditions selenate uptake across the brush-border membrane was reduced by oxalate and oxaloacetate but not by L-glutamate or L-leucine. Additionally sulphate uptake under this condition was significantly inhibited by oxalate (about 50%) and DIDS (25%). Sulphate transport by anion exchange was inhibited about 80% by both oxalate and DIDS. These results suggest that under Na⁺-gradient conditions sulphate (selenate) uptake in part occurs via anion exchange. Furthermore, oxalate seems to inhibit both Na⁺-sulphate (selenate) co-transport and sulphate (selenate) transport by anion exchange.

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