Skin vessel reactivity tests in healthy middle-aged and elderly subjects: the influence of depolarizating current and serum lipids.

Ten healthy, non-smoking subjects without atopic constitution, (eight males and two females, mean age 67.3 +/- 2.5 years), participated in a study of vascular reactivity. The subjects were tested with respect to apolipoprotein E alleles. Three vasodilating substances were iontophoresed into the skin, acetylcholine chloride (ACh); isoprenaline sulfate (isoprenaline); and sodium nitroprusside (SNP). ACh and isoprenaline were delivered to the anode, while SNP was delivered to the cathode. Also, 0.9% sodium chloride (NaCl) was delivered to the cathode in order to assess the effect of the iontophoretic current itself. The resultant vasodilation was mapped by a newly developed laser Doppler perfusion imager (LDPI) and correlated with fasting concentrations of serum lipids and lipoproteins. Skin vessel reactivity test to ACh, isoprenaline and SNP, but not NaCl, showed statistically significant negative correlations to the ratio LDL cholesterol/HDL cholesterol (P<0.05). The skin vessel responses to endothelium-dependent and possibly also to endothelium-independent substances are correlated with serum lipids and lipoproteins. It might be feasible to follow the effect of lipid-lowering strategies non-invasively with the aid of iontophoresis and laser Doppler perfusion imaging. The response to NaCl at the cathode might be due to a direct depolarizating effect on perivascular nerves and might thus be of interest when evaluating small nerve fiber dysfunction, for instance in diabetes mellitus.