Activation of Na+,H+ exchanger produces vasoconstriction of renal resistance vessels

Abstract

To evaluate the influence of the sodium/proton exchanger (Na+,H+ exchanger) on the constriction of rat resistance vessels and on the iliac artery, the isometric vasoconstrictions of renal resistance vessels and strips from iliac artery derived from Wistar-Kyoto rats were measured using a vessel myograph. The Na+,H+ exchanger was activated by intracellular acidification using propionic acid. Cytosolic pH (pHi) and cytosolic free sodium concentration ([Na+]i) in vascular smooth muscle cells were measured using the fluorescent dye technique. The activation of the Na+,H+ exchanger increased the [Na+]i by 12.4 +/- 1.3 mmol/L (n = 8). The activation of the Na+,H+ exchanger caused a contractile response of the renal resistance vessels (increase of tension, 1.5 +/- 0.1 x 10(-3) N; n = 13) and of the rat iliac artery (increase of tension, 7.5 +/- 0.8 x 10(-3) N; n = 5). The contractile response after activation of the Na+,H+ exchanger was significantly inhibited in the absence of external sodium or in the presence of amiloride, confirming the involvement of the Na+,H+ exchanger. The contractile response after activation of the Na+,H+ exchanger was significantly reduced in the absence of external calcium, after inhibition of calcium channels by nifedipine, and in the presence of an intracellular calcium antagonist 8-(diethylamino-)-octyl-3,4,5-trimethoxybenzoate (TMB-8), indicating that the activation of the Na+,H+ exchanger consecutively caused transplasma membrane calcium influx. On the other hand, the inhibition of the Na+,Ca2+ exchanger by NiCl2 significantly increased the vasoconstriction of renal resistance vessels after activation of the Na+,H+ exchanger. The activation of the Na+,H+ exchanger produces vasoconstriction by an increased cytosolic sodium concentration, inhibition of the Na+,Ca2+ exchanger, and activation of transplasma membrane calcium influx through potential dependent calcium channels.

Insulin sensitivity increase after calcium supplementation and change in intraplatelet calcium and sodium–hydrogen exchange in hypertensive patients with Type 2 diabetes1

“…Few studies have investigated the correlation between insulin concentration and NHE-1 change and their results are controversial [45][46][47]. In summary, in a study by Giordanno et al insulin resistance was not correlated with NHE-1 in Type 2 diabetes patients [45].…”

Effects of Copper Supplementation on the Structure and Content of Elements in Kidneys of Mosaic Mutant Mice

“…The absence of extracellular sodium diminishes the activity of sodium-dependent Cl − /HCO 3 − exchange [50], ultimately increasing Cl − content in the cytoplasm. X-ray microanalysis of proximal and distal tubular cells revealed a significant increase of Cl in ms/−(Cu) mice versus +/− animals.…”

Regulation of Trabecular Meshwork Contractility

“…In addition, endothelin has been shown to increase pH i in trabecular meshwork cells [102]. Considering that endothelin contracts trabecular meshwork cells, it is possible that pH i is involved in the signalling cascade leading to contraction of trabecular meshwork, in parallel to observations on other smooth muscle cells [117, 118]. …”