Effect of testosterone on carbonic anhydrase and MG(2+)-dependent HCO3-stimulated ATPase activities in rat kidney: comparison with estradiol effect

Gender differences in kidney function

Sex hormones influence the development of female (F) and male (M) specific traits and primarily affect the structure and function of gender-specific organs. Recent studies also indicated their important roles in regulating structure and/or function of nearly every tissue and organ in the mammalian body, including the kidneys, causing gender differences in a variety of characteristics. Clinical observations in humans and studies in experimental animals in vivo and in models in vitro have shown that renal structure and functions under various physiological, pharmacological, and toxicological conditions are different in M and F, and that these differences may be related to the sex-hormone-regulated expression and action of transporters in the apical and basolateral membrane of nephron epithelial cells. In this review we have collected published data on gender differences in renal functions, transporters and other related parameters, and present our own microarray data on messenger RNA expression for various transporters in the kidney cortex of M and F rats. With these data we would like to emphasize the importance of sex hormones in regulation of a variety of renal transport functions and to initiate further studies of gender-related differences in kidney structure and functions, which would enable us to better understand occurrence and development of various renal diseases, pharmacotherapy, and drug-induced nephrotoxicity in humans and animals.

Rat renal glucose transporter SGLT1 exhibits zonal distribution and androgen-dependent gender differences

SGLT1 (SLC5A1) mediates a part of glucose and galactose reabsorption in the mammalian proximal tubule (PT), but the detailed localization of the transporter along the tubule is still disputable. Here, we used several methods to localize rat SGLT1 (rSGLT1) in the kidneys of intact and variously treated male (M) and female (F) rats. In immunoblots of isolated cortical (C) and outer stripe (OS) brush-border membranes (BBM), a peptide-specific polyclonal antibody for rSGLT1 labeled a sharp inzone-, and gender-dependent ∼40-kDa protein and a broad ∼75-kDa band that exhibited strong zonal (OS > C) and gender differences (F > M). In tissue cryosections, the antibody strongly stained BBM of the S3 PT segments in the OS and medullary rays (F > M) and smooth muscles of the blood vessels and renal capsule (F ∼ M) and weakly stained the apical domain of other PT segments in the C (F ∼ M). The phlorizin-sensitive uptake of d-[3H]galactose in BBM vesicles, as well as the tissue abundance of rSGLT1-specific mRNA, matched the immunoblotting data related to the 75-kDa protein and the immunostaining in S3, proving zonal and gender differences in the functional transporter. Ovariectomy had no effect, castration upregulated, whereas treatment of castrated rats with testosterone, but not with estradiol or progesterone, downregulated the 75-kDa protein and the immunostaining in S3. We conclude that in the rat kidney, the expression of SGLT1 is represented by a 75-kDa protein localized largely in the PT S3 segments, where it exhibits gender differences (F > M) at both the protein and mRNA levels that are caused by androgen inhibition.