探讨多巴胺受体4(Drd4)缺失小鼠高血压的发病机制,我们测定了不同盐饮食的Drd4-/-和Drd4+/+小鼠的盐敏感性和肾钠转运蛋白。在正常NaCl饮食(NS)上,平均动脉压(MAP,遥测)在Drd4-/-中高于Drd4/-;低NaCl饮食(LS)倾向于降低两种菌株的MAP;相对于Drd4/-小鼠,高NaCl饮食(HS)升高的MAP,钠排泄减少,压力-利尿曲线向右移动。Drd4-/-小鼠表现出增加的肾钠氢交换剂3(NHE3),钠-钾-2-氯化物共转运蛋白(NKCC2),氯化钠协同转运蛋白(NCC),和NS上的外髓质α-上皮钠通道(αENaC),NKCC2,NCC,αENaC,和LS上的αNa+-K+-ATP酶,HS上的αENaC增加。NKCC2,NCC,αENaC,Drd4-/-血浆膜中的αNa-K-ATPase高于HS的Drd4/小鼠。D4R在近端和远端曲小管中表达,粗壮的上升肢体,与NKCC2和NCC共定位。在KO小鼠中,NKCC2的磷酸化增强,但泛素化减少。尽管随着饮食的变化,小鼠品系之间的血清醛固酮浓度和尿多巴胺排泄物没有差异。肾组织NHE3、NKCC2、NCC的mRNA表达,在Drd4-/-小鼠中NS上的αENaC没有改变。因此,Drd4-/-小鼠中NHE3、NKCC2、NCC和αENaC蛋白表达增加与高血压相关;NKCC2、NCC、αENaC,αNa+-K+-ATP酶可能介导Drd4-/-小鼠的盐敏感性。
To explore the mechanism of the hypertension in dopamine receptor-4 (Drd4) null mice, we determined the salt sensitivity and renal sodium transport proteins in Drd4-/- and Drd4+/+ mice with varied salt diets. On normal NaCl diet (NS), mean arterial pressures (MAP, telemetry) were higher in Drd4-/- than Drd4+/+; Low NaCl diet (LS) tended to decrease MAP in both strains; high NaCl diet (HS) elevated MAP with sodium excretion decreased and pressure-natriuresis curve shifted to right in Drd4-/- relative to Drd4+/+ mice. Drd4-/- mice exhibited increased renal sodium-hydrogen exchanger 3 (NHE3), sodium-potassium-2-chloride cotransporter (NKCC2), sodium-chloride cotransporter (NCC), and outer medullary α-epithelial sodium channel (αENaC) on NS, decreased NKCC2, NCC, αENaC, and αNa+-K+-ATPase on LS, and increased αENaC on HS. NKCC2, NCC, αENaC, and αNa+-K+-ATPase in plasma membrane were greater in Drd4-/- than in Drd4+/+ mice with HS. D4R was expressed in proximal and distal convoluted tubules, thick ascending limbs, and outer medullary collecting ducts and colocalized with NKCC2 and NCC. The phosphorylation of NKCC2 was enhanced but ubiquitination was reduced in the KO mice. There were no differences between the mouse strains in serum aldosterone concentrations and urinary dopamine excretions despite their changes with diets. The mRNA expressions of renal NHE3, NKCC2, NCC, and αENaC on NS were not altered in Drd4-/- mice. Thus, increased protein expressions of NHE3, NKCC2, NCC and αENaC are associated with hypertension in Drd4-/- mice; increased plasma membrane protein expression of NKCC2, NCC, αENaC, and αNa+-K+-ATPase may mediate the salt sensitivity of Drd4-/- mice.