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