AIM： To quantify changes in urinary excretion of aquaporin2 water channels （u-AQP2）, the sodium-potassium-chloride co-transporter （u-NKCC2） and the epithelial sodium channels （u-ENaC） during treatment with bend...AIM： To quantify changes in urinary excretion of aquaporin2 water channels （u-AQP2）, the sodium-potassium-chloride co-transporter （u-NKCC2） and the epithelial sodium channels （u-ENaC） during treatment with bendrofumethiazide （BFTZ）, amiloride and placebo.METHODS： In a randomized, double-blinded, placebo-controlled, 3-way crossover study we examined 23 healthy subjects on a standardized diet and fuid intake. The subjects were treated with amiloride 5 mg, BFTZ 1.25 mg or placebo twice a day for 4.5 d before each examination day. On the examination day, glomerular filtration rate was measured by the constant infusion clearance technique with 51Cr-EDTA as reference substance. To estimate the changes in water transport via AQP2 and sodium transport via NKCC2 and ENaC, u-NKCC2, the gamma fraction of ENaC （u-ENaCγ）, and u-AQP2 were measured at baseline and after infusion with 3% hypertonic saline. U-NKCC2, u-ENaCγ, u-AQP2 and plasma concentrations of vasopressin （p-AVP）, renin （PRC）, angiotensin Ⅱ （p-ANG Ⅱ） and aldosterone （p-Aldo） were measured, by radioimmunoassay. Central blood pressure was estimated by applanation tonometry and body fuid volumes were estimated by bio-impedance spectroscopy. General linear model with repeated measures or related samples Friedman’s two-way analysis was used to compare differences. Post hoc Bonferroni correction was used for multiple comparisons of post infusion periods to baseline within each treatment group.RESULTS： At baseline there were no differences in u-NKCC2, u-ENaCγ and u-AQP2. PRC, p-Ang Ⅱ and p-Aldo were increased during active treatments （P 〈 0.001）. After hypertonic saline, u-NKCC2 increased during amiloride （6% ± 34%; P = 0.081） and increased significantly during placebo （17% ± 24%; P = 0.010）. U-AQP2 increased signifcantly during amiloride （31% ± 22%; P 〈 0.001） and placebo （34% ± 27%; P 〈 0.001）, while u-NKCC2 and u-AQP2 did not change signifcantly during BFTZ （-7% ± 28%; P = 0.257 and 5% ± 16%; P = 0.261）. U- ENaCγ increased in all three groups （ P 〈 0.050）. PRC, AngⅡ and p-Aldo decreased to the same extent, while AVP increased, but to a smaller degree during BFTZ （ P = 0.048）. cDBP decreased significantly during BFTZ （P 〈 0.001）, but not during amiloride or placebo. There were no significant differences in body fuid volumes.CONCLUSION： After hypertonic saline, u-NKCC2 and u-AQP2 increased during amiloride, but not during BFTZ. Lower p-AVP during BFTZ potentially caused less stimulation of NKCC2 and AQP2 and subsequent lower reabsorption of water and sodium.展开更多
基金Supported by Grants from The Lundbeck FoundationAase and Ejnar Danielsens Foundation+1 种基金Helen and Ejnar Bjoernows FoundationRegion Midjutlands Research Fund
文摘AIM： To quantify changes in urinary excretion of aquaporin2 water channels （u-AQP2）, the sodium-potassium-chloride co-transporter （u-NKCC2） and the epithelial sodium channels （u-ENaC） during treatment with bendrofumethiazide （BFTZ）, amiloride and placebo.METHODS： In a randomized, double-blinded, placebo-controlled, 3-way crossover study we examined 23 healthy subjects on a standardized diet and fuid intake. The subjects were treated with amiloride 5 mg, BFTZ 1.25 mg or placebo twice a day for 4.5 d before each examination day. On the examination day, glomerular filtration rate was measured by the constant infusion clearance technique with 51Cr-EDTA as reference substance. To estimate the changes in water transport via AQP2 and sodium transport via NKCC2 and ENaC, u-NKCC2, the gamma fraction of ENaC （u-ENaCγ）, and u-AQP2 were measured at baseline and after infusion with 3% hypertonic saline. U-NKCC2, u-ENaCγ, u-AQP2 and plasma concentrations of vasopressin （p-AVP）, renin （PRC）, angiotensin Ⅱ （p-ANG Ⅱ） and aldosterone （p-Aldo） were measured, by radioimmunoassay. Central blood pressure was estimated by applanation tonometry and body fuid volumes were estimated by bio-impedance spectroscopy. General linear model with repeated measures or related samples Friedman’s two-way analysis was used to compare differences. Post hoc Bonferroni correction was used for multiple comparisons of post infusion periods to baseline within each treatment group.RESULTS： At baseline there were no differences in u-NKCC2, u-ENaCγ and u-AQP2. PRC, p-Ang Ⅱ and p-Aldo were increased during active treatments （P 〈 0.001）. After hypertonic saline, u-NKCC2 increased during amiloride （6% ± 34%; P = 0.081） and increased significantly during placebo （17% ± 24%; P = 0.010）. U-AQP2 increased signifcantly during amiloride （31% ± 22%; P 〈 0.001） and placebo （34% ± 27%; P 〈 0.001）, while u-NKCC2 and u-AQP2 did not change signifcantly during BFTZ （-7% ± 28%; P = 0.257 and 5% ± 16%; P = 0.261）. U- ENaCγ increased in all three groups （ P 〈 0.050）. PRC, AngⅡ and p-Aldo decreased to the same extent, while AVP increased, but to a smaller degree during BFTZ （ P = 0.048）. cDBP decreased significantly during BFTZ （P 〈 0.001）, but not during amiloride or placebo. There were no significant differences in body fuid volumes.CONCLUSION： After hypertonic saline, u-NKCC2 and u-AQP2 increased during amiloride, but not during BFTZ. Lower p-AVP during BFTZ potentially caused less stimulation of NKCC2 and AQP2 and subsequent lower reabsorption of water and sodium.
