Leucocyte intracellular pH and Na+/H+ antiport activity in human hypertension

Hypertension is associated with thickening of the wall of resistance vessels, but the cellular or genetic basis of this is unclear. Cell proliferation and intracellular alkalinization via increased Na+/H+ exchange are linked in the response of tissues to growth factors. To define a possible cellular basis for vascular medial thickening in hypertension, we studied leucocyte intracellular pH, buffering power and Na+/H+ antiport activity in 17 hypertensive and 17 age-, sex- and weight-matched normotensive subjects. The cells from hypertensive subjects were significantly more alkaline [median (range): 7.49 (7.26-7.95) versus 7.39 (7.25-7.53); P less than 0.01], and had a lower buffering power [8.95 (3.05-17.98) versus 12.57 (7.44-19.95) mmol/l per pH unit; P less than 0.02] than those from normotensive subjects. Moreover, the activity of the Na+/H+ antiport was higher when cells were acid-loaded to an intracellular pH of 6.7. The presence of a similar increased activity in vascular smooth muscle cells may be associated with increased cellular proliferation resulting in a thickened media or increased vascular smooth muscle contractility.