Abstract: Objective:To investigate the effect of high salt diet on the arterial blood pressure in the urea transporter B(UT-B) gene depletion (UT-B ^-/-) mice, and to clarify the possible mechanism of the UT-B^-/- leading to the changes in the arterial blood pressure of the mice. Methods:The heterozygous (UT-B^+/-) mice were mated to obtain the wild-type (UT-B^+/+) and UT-B^-/- mice with the same genetic background. The 4-week-old male UT-B^+/+ and UT-B^-/- mice were selected and fed on normal diet (0.3% NaCl) or high salt diet (8.0% NaCl) for 4 weeks. The mice were divided into UT-B^+/+ mice+normal diet (UT-B^+/++N) group,UT-B^-/- mice +normal diet (UT-B^-/-+N) group,UT-B^+/+ mice+high salt diet(UT-B^+/++H) group,and UT-B^-/- mice+high salt diet(UT-B^-/-+H) group. The changes in water intakes and mean arterial pressures of the mice in various groups were monitored; RT-PCR, Western blotting and immunohistochemistry were used to detect the expression levels and location of UT-B mRNA and protein in choroid plexus(CP) of the brain tissue of the mice. The levels of serum angiotensin Ⅱ (Ang Ⅱ) and the Na⁺ levels in cerebrospinal fluid of the mice in various groups were determined by ELISA. Results:The PCR results of genomic DNA of mouse tail showed that there was a 400 bp base fragment in the UT-B^+/+ mice, 250 and 400 bp base fragments in the UT-B^+/- mice, and 250 bp base fragment in the UT-B^-/- mice. Compared with normal salt diet group, the water intake of the mice in high salt diet was significantly increased (P<0.01); compared with UT-B^-/-+N group and UT-B^+/++H group,the mean arterial pressure of the mice in UT-B^-/-+H group was significantly increased(P<0.01).The UT-B mRNA and protein expressed in the epithelial cells of CP in the UT-B^+/+ mice. Compared with UT-B^-/-+N group and UT-B^+/+ mice+H group, the Ang Ⅱ level in serum of the mice in UT-B^-/- mice+H group was significantly increased (P<0.01); the Na⁺ level in cerebrospinal fluid of the mice was significantly increased (P<0.05). Conclusion:High salt diet can cause a significant increase in the mean arterial pressure in the UT-B^-/- mice, and its mechanism is related to increasing the serum Ang Ⅱ level and the Na⁺ level in cerebrospinal fluid in the mice.

Key words: high salt diet, urea transporter B, mean arterial pressure, cerebrospinal fluid, sodium ion