Songu-Mize E, Caldwell R W, Baer P G
Department of Pharmacology, University of Tennessee at Memphis 38163.
Proc Soc Exp Biol Med. 1987 Dec;186(3):280-7. doi: 10.3181/00379727-186-42614.
Studies of renal and other tissues suggest that chronic elevation or reduction of dietary potassium intake could affect vascular smooth muscle sodium pump (Na-pump) activity. To examine this possibility, the effects of 3 weeks of low (LK: 4 mmole KCl/kg chow), normal (NK; 162 mmole/kg), and high (HK; 1350 mmole/kg) dietary potassium intake on Na-pump activity, the Na-pump activity response to changes in extracellular potassium concentration, and Na-pump site density were determined in tail arteries of rats. Plasma potassium concentration was elevated by 21% in HK rats and reduced by 45% in LK rats. When incubated in autologous plasma, compared to arteries from NK rats, Na-pump activity was decreased in the tail arteries from LK rats but not altered in those from HK rats. When arteries from NK and LK rats were incubated in autologous plasma with the potassium concentration increased to equal that of the HK rats, Na-pump activity exceeded that of HK rat arteries: Na-pump activity of arteries incubated in autologous plasma did not differ from that of arteries incubated in Krebs-Henseleit buffer with the potassium concentration adjusted to equal that of the plasma. Tail artery Na-pump activity for all three dietary potassium groups increased as potassium concentration of the incubation medium was increased from 1 to 12 mM; Na-pump activity was similar for the NK and LK rats at all potassium concentrations, but Na-pump activity of HK rat arteries was less than that of NK arteries at high extracellular potassium concentrations. Na-pump site density was not altered by either HK or LK diet. It is concluded that in tail arteries of rats fed the LK diet, chronically decreased extracellular potassium results in chronically decreased Na-pump activity. In contrast, an adaptive change occurs in tail arteries of rats fed HK diet, such that Na-pump activity remains at normal levels despite elevated extracellular potassium; this adaptive response to chronically increased dietary potassium does not appear to be the result of decreased Na-pump site density.
对肾脏及其他组织的研究表明，长期提高或降低饮食中钾的摄入量可能会影响血管平滑肌钠泵（Na泵）的活性。为了验证这种可能性，研究人员测定了低（LK：4毫摩尔氯化钾/千克食物）、正常（NK；162毫摩尔/千克）和高（HK；1350毫摩尔/千克）三种饮食钾摄入量持续3周对大鼠尾动脉中Na泵活性、Na泵对细胞外钾浓度变化的反应以及Na泵位点密度的影响。HK组大鼠的血浆钾浓度升高了21%，LK组大鼠的血浆钾浓度降低了45%。与NK组大鼠的动脉相比，当在自体血浆中孵育时，LK组大鼠尾动脉中的Na泵活性降低，而HK组大鼠尾动脉中的Na泵活性未发生改变。当NK组和LK组大鼠的动脉在自体血浆中孵育，且钾浓度升高至与HK组大鼠相同时，Na泵活性超过了HK组大鼠动脉：在自体血浆中孵育的动脉的Na泵活性与在钾浓度调整至与血浆相同的Krebs-Henseleit缓冲液中孵育的动脉的Na泵活性没有差异。随着孵育培养基中钾浓度从1毫摩尔/升增加到12毫摩尔/升，所有三个饮食钾组的尾动脉Na泵活性均增加；在所有钾浓度下，NK组和LK组大鼠的Na泵活性相似，但在高细胞外钾浓度下，HK组大鼠动脉的Na泵活性低于NK组动脉。HK饮食或LK饮食均未改变Na泵位点密度。研究得出结论，在喂食LK饮食的大鼠尾动脉中，细胞外钾长期降低导致Na泵活性长期降低。相比之下，喂食HK饮食的大鼠尾动脉会发生适应性变化，使得尽管细胞外钾升高，Na泵活性仍保持在正常水平；这种对长期增加饮食钾的适应性反应似乎不是Na泵位点密度降低的结果。
