engleski

Organic anion transporter Oat2 in rat and mouse proximal tubules exhibits gender differences largely due to androgen inhibition

The renal reabsorption and/or excretion of various endogenous and xenobiotic organic anions is mediated by specific cell membrane transporters (Oat). Oat2 (Slc22a7) has been identified in rat kidney, where its mRNA expression exhibits gender differences (females (F)>males (M)). However, the exact localization of Oat2 protein in the rat or other mammalian kidney has not been reported. In this work we investigated the expression of Oat2 mRNA by RT-PCR and its protein by Western blotting (WB) and immunocytochemistry (IC) in kidneys of adult intact and gonadectomized M and F, sex hormone-treated castrated M, and prepubertal intact M and F rats, and localized the renal protein in adult M and F mice. In the kidney of adult rats, the expression of Oat2 mRNA was predominant in the outer stripe (OS) tissue, where it exhibited: a) clear gender dependency (F>M), b) upregulation by castration in M, and downregulation by ovariectomy in F, and c) strong downregulation by testosterone-, and weak upregulation by estradiol- and progesterone-treatment in castrated M. A rabbit-raised polyclonal antibody against the specific peptide of the rat Oat2 on WB of isolated renal membranes labeled a single ~66 kDa protein band, that was much stronger in F. By IC, the antibody exclusively stained brush-border (BB) of the proximal tubule S3 segment in the OS and medullary rays, brightly in F and poorly in M. In variously treated rats, the pattern of 66 kDa band density in the OS membranes and the staining intensity of BB in S3 segments completely matched the mRNA expression. The expression of Oat2 protein in prepubertal rats was low and gender-independent, whereas in mice, the expression pattern largely resembled that in rats. Therefore, Oat2 in rat (and mouse) kidney is localized to the BB of proximal tubule S3 segments, where it exhibits gender differences (F>M) that appear in puberty and are caused by strong androgen inhibition and weak estrogen and progesterone stimulation.

sex differences; testosterone; membrane transport; organic anions; steroid hormones

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