Sex-dependent expression of water channel AQP1 along the rat nephron.

In the mammalian kidney, nonglycosylated and glycosylated forms of aquaporin protein 1 (AQP1) coexist in the luminal and basolateral plasma membranes of proximal tubule and descending thin limb. Factors that influence AQP1 expression in (patho)physiological conditions are poorly known. Thus far, only angiotensin II and hypertonicity were found to upregulate AQP1 expression in rat proximal tubule in vivo and in vitro (Bouley R, Palomino Z, Tang SS, Nunes P, Kobori H, Lu HA, Shum WW, Sabolic I, Brown D, Ingelfinger JR, Jung FF. Am J Physiol Renal Physiol 297: F1575-F1586, 2009), a phenomenon that may be relevant for higher blood pressure observed in men and male experimental animals. Here we investigated the sex-dependent AQP1 protein and mRNA expression in the rat kidney by immunochemical methods and qRT-PCR in tissue samples from prepubertal and intact gonadectomized animals and sex hormone-treated gonadectomized adult male and female animals. In adult rats, the overall renal AQP1 protein and mRNA expression was ∼80% and ∼40% higher, respectively, in males than in females, downregulated by gonadectomy in both sexes and upregulated strongly by testosterone and moderately by progesterone treatment; estradiol treatment had no effect. In prepubertal rats, the AQP1 protein expression was low compared with adults and slightly higher in females, whereas the AQP1 mRNA expression was low and similar in both sexes. The observed differences in AQP1 protein expression in various experiments mainly reflect changes in the glycosylated form. The male-dominant expression of renal AQP1 in rats, which develops after puberty largely in the glycosylated form of the protein, may contribute to enhanced fluid reabsorption following the androgen- or progesterone-stimulated activities of sodium-reabsorptive mechanisms in proximal tubules.

Sex-independent expression of chloride/formate exchanger Cfex (Slc26a6) in rat pancreas, small intestine, and liver, and male-dominant expression in kidneys.

Chloride/formate exchanger (CFEX; SLC26A6) mediates oxalate transport in various mammalian organs. Studies in Cfex knockout mice indicated its possible role in development of male-dominant hyperoxaluria and oxalate urolithiasis. Rats provide an important model for studying this pathophysiological condition, but data on Cfex (rCfex) localisation and regulation in their organs are limited. Here we applied the RT-PCR and immunochemical methods to investigate rCfex mRNA and protein expression and regulation by sex hormones in the pancreas, small intestine, liver, and kidneys from intact prepubertal and adult as well as gonadectomised adult rats treated with sex hormones. rCfex cDNA-transfected HEK293 cells were used to confirm the specificity of the commercial anti-CFEX antibody. Various biochemical parameters were measured in 24-h urine collected in metabolic cages. rCfex mRNA and related protein expression varied in all tested organs. Sex-independent expression of the rCfex protein was detected in pancreatic intercalated ducts (apical domain), small intestinal enterocytes (brush-border membrane; duodenum > jejunum > ileum), and hepatocytes (canalicular membrane). In kidneys, the rCfex protein was immunolocalised to the proximal tubule brush-border with segment-specific pattern (S1=S2