Renal expression of organic anion transporter Oat5 in rats and mice exhibits the female-dominant sex differences
Davorka Breljak1, Marija Ljubojević1, Daniela Balen1, Vilim Žlender1, Hrvoje Brzica1, Vedran Micek1, Marija Kušan1*, Naohiko Anzai2 and Ivan Sabolić1
1Molecular Toxicology, Institute for Medical Research and Occupational Health, Zagreb, Croatia and 2Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Tokyo, Japan
*Present address: Psychiatric Hospital Vrapče, Zagreb, Croatia.
Offprint requests to: Ivan Sabolić, M.D., Ph.D., Molecular Toxicology, Institute for Medical Research and Occupational Health, Ksaverska cesta 2, 10001 Zagreb, Croatia. e-mail: email@example.com
Summary. The organic anion transporter 5 (Oat5, Slc22a19) was previously localized to the brush-border of proximal tubule (PT) S3 segment in rat and mouse kidneys. Here we report on sex hormone-regulated expression of Oat5 in rat kidneys, after reinvestigating: a) expression of its mRNA by end-point and real time RT-PCR in the tissue, b) abundance of its protein by Western blotting (WB) in isolated membranes, and c) immunolocalization in tissue cryosections. In untreated male (M) and female (F) adult rats, the expression of Oat5 mRNA was predominant in the outer stripe (OS), exhibiting sex differences (M<F), upregulated by castration, and unaffected by ovariectomy. In castrated M, testosterone treatment strongly downregulated, whereas estradiol and progesterone treatment weakly upregulated its expression. By WB, a single protein band of ~72 kDa in variously-treated animals exhibited a density pattern comparable to that of mRNA. By immunostaining, Oat5 protein was localized to the brush-border of S1/S2 in the cortex (CO) (weakly) and in S3 of the OS and medullary rays (strongly) with the F-dominant intensity. In variously-treated rats, the immunostaining pattern matched that of mRNA and WB data. In prepubertal rats, the renal expression of Oat5 mRNA and protein was weak and sex-independent. In adult mice, the sex-dependent pattern of renal Oat5 protein expression was comparable to that in rats. Therefore, the renal expression of Oat5 in rats (and mice) exhibits zonal (CO<OS) and sex differences (M<F), which appear after puberty, largely due to androgen-driven downregulation of its mRNA and protein expression. Histol Histopathol 25, 1385-1402 (2010)
Key words: Gender differences, Kidney, Membrane transporters, Organic anions, Proximal tubule