engleski

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

The sulfate anion transporter (sat-1, Slc26a1) has been cloned from rat liver, functionally characterized, and in rats localized to the basolateral cell membrane in renal proximal tubules and sinusoidal cell membrane in hepatocytes. In this work we confirm previously described localization in liver cells, and report on sex differences (SD) in sat-1 protein expression in the rat liver detected by immunocytochemistry in tissue cryosections, Western blotting, and transport studies in isolated total cell membranes. The sat-1-related ~85 kDa protein was localized exclusively to the hepatocyte sinusoidal membranes, where it showed a male (M)-dominant expression. In transport studies, isolated membrane vesicles from M liver exhibited a significantly higher uptake of radiolabeled sulfate in exchange for oxalate than the membranes from female (F) liver. However, the real-time RT-PCR data indicated an absence of SD at the level of sat-1 mRNA. In further studies, the expression of liver sat-1 protein was: (a) unaffected by castration, b) up-regulated by ovariectomy, and (c) down-regulated by estrogen- or progesterone-treatment in M. We conclude that SD (M>F) in the abundance of liver sat-1 transporter in rats are caused by the F sex hormones-driven inhibition of protein expression at the post-transcriptional level. A higher expression of sat-1 protein in the hepatocytes of M rats may conform to elevated uptake of sulfate and extrusion of oxalate. The extruded oxalate, being secreted by the renal proximal tubules, may contribute to the development of oxalate urolithiasis, which occurs more often in M.

castration; gender differences; immunocytochemistry; oxalate; sex hormones; urolithiasis; immunoblotting

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