Multispecific anion exchange in basolateral (sinusoidal) rat liver plasma membrane vesicles

Abstract

The mechanisms and driving forces for hepatic uptake of sulfate were investigated in basolateral (sinusoidal) rat liver plasma membrane vesicles. A transmembrane pH difference (pH 8.0 inside, 6.0 outside) stimulated sulfate uptake above equilibrium ("overshoot"). This pH gradient-stimulated sulfate uptake was saturable with increasing concentrations of sulfate and could be inhibited by probenecid, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), carbonyl cyanide p-(trifluoromethoxy)-phenylhydrazone, and nigericin. At low buffer concentrations and pH 6.0 an inwardly directed sodium gradient also stimulated sulfate uptake. This sodium-dependent sulfate uptake could be inhibited by amiloride and DIDS, indicating indirect coupling of sodium and sulfate flux through concomitant sodium-proton and sulfate-hydroxyl exchange. Cisinhibition of initial pH gradient-stimulated sulfate uptake, as well as transstimulation of sulfate uptake under pH-equilibrated conditions (pH 7.5 inside and outside), were observed with sulfate, thiosulfate, oxalate, and succinate, but not with chloride, bicarbonate, acetate, lactate, pyruvate, p-aminohippurate, citrate, glutamate, aspartate, and taurocholate. Furthermore, cholate and sulfobromophthalein exhibited competitive inhibition of pH gradient-stimulated sulfate uptake. In addition, an inside-to-outside hydroxyl gradient also stimulated uptake of cholate and this pH gradient-sensitive portion of cholate uptake was inhibited by extravesicular sulfate. In contrast to basolateral membranes, no evidence for multispecific sulfate-hydroxyl exchange was found in canalicular plasma membrane vesicles.

Oxalate: From the Environment to Kidney Stones

“…Hepatocytes utilize substantial SO 4 2-in various detoxifi cation and sulfation reactions. The SO 4 2-/anion exchange system that transports various anions including oxalate was demonstrated in the sinusoidal (114,115,121 membrane of rat hepatocytes (129). In support of these fi ndings, Sat-1, an exchanger of SO 4 2-and an oxalate, was localized in rats to the hepatocyte sinusoidal membrane (116,117,130).…”

Transport of organic anions in the liver. An update on bile acid, fatty acid, monocarboxylate, anionic amino acid, cholephilic organic anion, and anionic drug transport

“…1981; Van Dyke et al t982b; Ohkuma et al 1983;Petzinger and Frimmer 1988;F611mann et al 1990), and basolateral (sinusoidal) membrane vesicles from rat liver Hugentobler and Meier 1986;Caflish et al 1990) and skate liver . In most studies saturable, energy-dependent, and temperature-sensitive uptake was found.…”

“…Stoichiometries of cotransports are hard to verify in living intact cells. Therefore uptake studies with basolateral membrane vesicles were performed which unfortunately led to doubts about the presence of a sodium-CA cotransport in vesicles (Hugentobler and Meier 1986;Blitzer et al 1986). Instead, pH driven proton/CA cotransport analogous with hydroxyl/CA exchange ) as well as a sulfate/hydroxyl exchanger with binding properties for CA (Hugentobler and Meier 1986) was postulated to account for hepatocellular CA uptake.…”

“…The pH gradient driven bite acid uptake into the vesicles was not observed for TCA, CDCA or DCA. An important difference appears between uptake studies in vesicles and those in intact cells: in membrane vesicles pH-dependent CA uptake was not inhibited by 15 mM 4,4'-diisothiocyanato-2,2'-disulfonic acid stilbene (DIDS;Btitzer et al 1986;Hugentobler et al 1987), although DIDS irreversibly inhibited hepatocellular CA and phalloidin uptake and sulfate/hydroxyl exchange (Hugentobler and Meier 1986). Recently, both pH-dependent and sodium-dependent uptake of CA was described in basolateral plasma membrane vesicles from rat liver (Caflish et al 1990).…”

The liver and kidney expression of sulfate anion transporter sat-1 in rats exhibits male-dominant gender differences

“…However, the kinetic studies in rats indicated that, in the liver, sulfate is also transcellularly transported and concentrated in the bile, 10-15-fold above the intracellular sulfate concentration [35]. The major players involved in these processes seem to be the two Na + -independent anion transporters, the lowaffinity sulfate-anion (chloride, thiosulfate, oxalate, succinate, cholate) exchanger in the hepatocyte sinusoidal membrane (sat-1; K m for sulfate ∼16 mM) and a highaffinity sulfate-anion (bicarbonate, thiosulfate, oxalate) exchanger in the canalicular membrane (K m for sulfate 0.3 mM) [14,30]. In kidneys, sulfate is freely filtered.…”