Ellstrom D R, Honeyman T W, Scheid C R
Department of Physiology, University of Massachusetts Medical School, Worcester 01655.
Am J Hypertens. 1994 Apr;7(4 Pt 1):340-5. doi: 10.1093/ajh/7.4.340.
Na+/H+ exchange differs kinetically in mesenteric arteries from spontaneously hypertensive rats (SHR). Both the maximal transport rate and the sensitivity to [H+]i are greater in SHR than in Wistar Kyoto (WKY) rats. Kinetic changes are not seen in prehypertensive SHR or in SHR rendered normotensive by captopril therapy. Thus, blood pressure affects the properties of Na+/H+ exchange in SHR. To determine whether elevated pressure would have similar effects on the WKY transporter, WKY rats were rendered hypertensive by treatment with deoxycorticosterone acetate (DOCA). Mesenteric arteries from these animals were loaded with the pH-sensitive dye BCECF and Na+/H+ exchange activity was assessed by measuring the Nao-dependent, dimethyl amiloride-sensitive recovery of intracellular pH after acid loading. Treatment with DOCA/salt (two injections of 30 mg of DOCA/kg per week for 4 weeks + 1% NaCl in the drinking water) produced a significant increase in mean arterial pressure (181 +/- 29 v 108.1 +/- 6.2 in DOCA/salt v untreated controls), but had no effect on Na+/H+ exchange. Maximal transport rates for untreated, DOCA/salt-treated, and salt-treated rats were virtually identical (0.088 +/- 0.001, 0.103 +/- 0.011, and 0.093 +/- 0.006 mmol/L H+/sec, respectively. Moreover, the sensitivity of Na+/H+ exchange to internal H+ (ie, the Hill coefficient) was unchanged (n(app) = 4.3, 3.7, and 4.0, respectively). Because elevation in blood pressure produced no significant alterations in the WKY Na+/H+ exchanger, it seems likely that there are strain differences in the exchanger and/or in processes regulating its activity.
钠氢交换在自发性高血压大鼠（SHR）肠系膜动脉中的动力学存在差异。与Wistar Kyoto（WKY）大鼠相比，SHR的最大转运速率和对细胞内氢离子浓度（[H⁺]i）的敏感性均更高。在高血压前期的SHR或通过卡托普利治疗使血压恢复正常的SHR中未观察到动力学变化。因此，血压会影响SHR中钠氢交换的特性。为了确定血压升高是否会对WKY转运体产生类似影响，通过给予醋酸脱氧皮质酮（DOCA）使WKY大鼠患高血压。给这些动物的肠系膜动脉加载对pH敏感的染料BCECF，并通过测量酸负荷后细胞内pH值依赖于钠离子（Nao）、对二甲苯酰胺敏感的恢复情况来评估钠氢交换活性。给予DOCA/盐（每周两次注射30mg/kg DOCA，共4周 + 饮水中含1% NaCl）可使平均动脉压显著升高（DOCA/盐组为181±29，未治疗对照组为108.1±6.2），但对钠氢交换无影响。未治疗、DOCA/盐治疗和盐治疗大鼠的最大转运速率几乎相同（分别为0.088±0.001、0.103±0.011和0.093±0.006 mmol/L H⁺/秒）。此外，钠氢交换对细胞内氢离子的敏感性（即希尔系数）未改变（表观值分别为4.3、3.7和4.()）。由于血压升高并未使WKY钠氢交换体发生显著改变，因此，交换体本身和/或调节其活性的过程可能存在品系差异。
