engleski

Expression of aquaporin 1 along the rat nephron is sex dependent

Aquaporin 1 (AQP1) is a constitutive water channel in proximal tubules and descending thin limbs, where it exists in both nonglycosylated (NG) and glycosylated (G) forms. Both forms are functional. Physiological conditions that may influence AQP1 expression along the nephron have been poorly studied. To reveal possible effects of gender on renal AQP1 expression, we performed: a) immunofluorescence cytochemistry in various kidney zones (cortex, outer stripe, inner stripe, papilla) from adult male and female rats, and b) Western blotting (WB) of total cell membranes from various kidney zones of the adult, pre-pubertal, and gonadectomized rats, brush-border and basolateral membranes isolated from the cortex and outer stripe from adult rats, as well as red blood cell plasma membranes from adult rats. Quantitative immunocytochemistry revealed 23%, 37%, 48%, and 33% more AQP1-related immunofluorescence (average pixel intensity) in the cortex, outer stripe, inner stripe, and papilla, respectively, of males vs. females (P<0.05). These findings were confirmed by WB in total cell membranes and in isolated brush-border and basolateral membranes from the respective kidney zones: the total abundance of AQP1 (NG+G) in the tissues and isolated membranes was higher in males. However, the differences in renal AQP1 expression were restricted to the G form of the protein. Similar sex differences in the abundance of AQP1 were absent in total cell membranes from various kidney zones in pre-pubertal (3-week-old) rats and in red blood cell plasma membranes from adult rats. Following gonadectomy in adult rats, the expression of AQP1 (both forms) in total cell membranes from various kidney zones did not change in males, whereas in females, the G form was increased in the outer stripe. We conclude that: a) sex differences exist in the expression of AQP1 along the rat nephron (male>female), b) these differences are confined to the G form of AQP1, and c) the state of glycosylation of AQP1 may be affected (probably inhibited) by ovarian hormones.

gender differences; immunocytochemistry; kidney; water channels

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