engleski

Gender differences in rat renal Na+-glucose cotransporter SGLT1

Objective. SGLT1 mediates a part of glucose and galactose reabsorption in the mammalian nephron. Previous transport studies in isolated brush-border membranes (BBM) from various kidney regions, and hybridization studies in the kidney tissue from rats and rabbits, localized this transporter largely to the proximal tubule (PT) S3 segments in the outer stripe (OS) and medullary rays (MR). However, due to lack of good antibodies, the immunolocalization of SGLT1 along the mammalian nephron still awaits clarification. Methods. In this work we used a polyclonal antibody against the peptide specific for rat SGLT1, and studied the transporter along the nephron of male (M) and female (F) rats by Western blotting (WB) of BBM isolated from the kidney cortex (C) and OS, and by immunocytochemistry (IC) in tissue cryosections. These findings were correlated with the Na+-dependent, phlorizin-inhibitable uptake of 3H-D-galactose in the BBM vesicles, tested by rapid filtration technique, and with the abundance of specific mRNA in the C and OS tissue, determined by Northern blotting. Results. In WB of BBM, the antibody labeled two major protein bands: the abundance of a sharp, ~40 kDa band was not zone- and gender-dependent, whereas the abundance of a broad, ~75 kDa band in both sexes exhibited strong zonal (OS>C) and gender differences (F>M). By IC, the antibody stained strongly the S3 BBM in the OS and MR, and smooth muscles in blood vessels and renal capsule, and weakly the apical domain of other PT segments in the C. Strong gender differences (F>M) in the staining intensity were observed in S3 in the OS and MR, but not in the blood vessels. The phlorizin-sensitive uptake of 3H-D-galactose in BBM vesicles completely matched the WB data related to the 75 kDa band and the IC data, proving zonal and gender differences in the transporter activity. Relevant gender differences (F>M) were also found for the specific mRNA in the OS but not in the C. Conclusions. We conclude that in the rat kidney, the expression of SGLT1 is represented by 75 kDa protein localized largely in the S3, where it exhibits gender differences (F>M) at both protein and mRNA level.

kidney; membrane transporters; sex differences

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