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Free keywords:
Na+-H+ exchange; Acridine orange; Steroid hormone; Membrane vesicle; (Mouse kidney)
Abstract:
Na+-H+ exchange in rat and mouse renal brush-border membrane vesicles was studied by fluorescence quenching of the ΔpH indicator, acridine orange. Brush-border membrane vesicles were isolated by a modified Mg/EGTA-precipitation method at low speed centrifugation (8000 × g). The enzymatic characteristics of these membrane vesicles were similar to those obtained by the original high-speed centrifugation method (Biber et al. (1981) Biochim. Biophys. Acta, 647, 169–176). The rates of Na+-H+ exchange in renal brush-border membrane vesicles from male and female rats were similar. Neither ovariectomy nor treatment of ovariectomized rats with estradiol or testosterone changed the activity of Na+-H+ exchanger. The rates of Na+-H+ exchange in the mouse were smaller than in the rat indicating the existence of species differences. Na+-H+ exchange in mouse renal brush-border membranes exhibit strong sex differences, the rates in the male being higher than in the female. Castration of male mice led to a decrease in Na+-H+ exchanges to values found in females. Treatment of castrated mice with estradiol had no effect. In contrast, treatment with testosterone increased the rat of the exchanger by more than 100%. The effect of testosterone was restricted to the Vmax of the Na+-H+ exchanger, whereas the apparent Km for Na+ remained unchanged. Na+-dependent d-glucose transport in mouse renal luminal membranes exhibited also sex differences due to the potent stimulatory effect of testosterone. Therefore, Na+-H+ exchange and Na+-dependent d-glucose transport in the mouse kidney are under control of androgen hormones. This effect could be in close connection with the wellknown renotropic action of androgens in the mouse.
