Exogenous zinc improves blood fluidity but has no effect on the mechanisms of vascular response to acetylcholine iontophoresis in humans.
ABSTRACT Recent findings in cellular signaling function of zinc through the mobilization intracellular calcium or by inducing ATP release suggest that extracellular zinc plays an important role in many physiological functions. However, such an extracellular signaling action of zinc for most cells is not known. Therefore, we investigated whether zinc plays any role in endothelium- dependent acetylcholine (ACh)-induced vasodilatation in microvascular beds. Transdermal iontophoresis was used to transport ACh through the forearm skin and cutaneous perfusion was measured using a laser Doppler flowmeter (LDF). Experiments were repeated using (1) zinc instead of ACh to test the effect of zinc ions alone and (2) concomitant iontophoresis of ACh and zinc to explore the effect of zinc on ACh-induced vasodilatation. Although zinc augments blood flow, curve-fitting to LDF signals indicate that zinc has no effect on the neural and endothelial component of ACh-induced vasodilatation. Additionally, no effect of Zn2+ on blood flow was found during its iontophoresis alone. Therefore, it is suggested from the Fourier analysis of LDF signals that the Zn+ might influence blood fluidity by its action on red blood cells deformability/ aggregability during a high-blood-flow condition, which might, in turn, decrease blood viscosity and improve blood flow in vivo.