THE EFFECT OF IONTOPHORESIS ON THE CUTANEOUS VASCULATURE - EVIDENCE FOR CURRENT-INDUCED HYPEREMIA

Combining laser-Doppler blood flux measurements of the skin microcircu lation with iontophoresis of vasoactive agents is a promising noninvas ive tool for pharmacological studies. However, preliminary observation s in our laboratories suggested significant current-associated vasodil ation when an expected vasoconstrictor (N-G-monomethyl-L-arginine acet ate) was iontophoresed. The present study was designed to define nonsp ecific current-related versus specific pharmacological effects of iont ophoretically administered ions on the cutaneous vasculature. Dose-res ponse studies to a series of anions (nitrite, chloride, acetate, and b icarbonate) and cations (sodium, lithium, and acetylcholine) were carr ied out in six healthy volunteers (three male) by iontophoresis to the forearm skin on separate days. Laser-Doppler flux was measured at the same sires. All ions caused dose-dependent vasodilation, There was no difference in the response between chloride, bicarbonate, or acetate and nitrite, the nitric oxide donor. The acetylcholine dose response w as shifted rightward after atropine pretreatment. Cutaneous vascular r esponses to iontophoresis comprise nonspecific, current-induced hypere mia and specific effects of the administered agent. Acetylcholine appe ars to cause muscarinic and current-induced dilatation. Nitrite may ca use current-induced hyperemia alone. Current-induced hyperemia should be considered in interpreting the acute cutaneous vascular responses t o iontophoretically administered agents in humans. (C) 1995 Academic P ress, Inc.