Laser Doppler imager (LDI) scanner and intradermal injection for in vivo pharmacology in human skin microcirculation: responses to acetylcholine, endothelin‐1 and their repeatability

Abstract

AimsThe purpose of this study was to evaluate the repeatability of forearm skin blood fl ow responses to intradermal injections of acetylcholine (ACh) and endothelin-1 (ET-1) using a double injection technique (DIT) and a laser Doppler imager (LDI) scanner in the human skin microcirculation. MethodsWe used a laser Doppler imager (Moor LDI V3.01) to continuously monitor the change in skin blood flow during intradermal administration of physiological saline (0.9% NaCl), acetylcholine (ACh 10 -7 , 10 -8 , 10 -9 M) and endothelin-1 (ET-1 10 -14 , 10 -16 , 10 -18 M) in 10 healthy male subjects. Subjects were examined on 3 different days for assessment of interday and interobserver repeatability. Injections of either drug were randomly placed on different sites of the forearm. Laser Doppler images were collected before and after injection at 2.5 min intervals for 30 min. Data were analysed after the completion of each experiment using Moor Software V.3.01. Results are expressed as changes from baseline in arbitrary perfusion units (PU). ResultsACh caused a significant vasodilation ( P < 0.0001 ANOVA , mean ± SE: 766 ± 152 PU, ACh 10 -9 M; 1868 ± 360 PU, ACh 10 -8 M; 4188 ± 848 PU, ACh 10 -7 M; mean of days 1 and 2, n = 10), and ET-1 induced a significant vasoconstrictive response ( P < 0.0001 ANOVA , -421 ± 83 PU, ET-1 10 -18 M; -553 ± 66 PU, ET-1 10 -16 M; -936 ± 90 PU, ET-1 10 -14 M; mean of days 1 and 2, n = 10). There was no difference on the response to either drug on repeated days. Bland-Altman analyses showed a close agreement of responses between days with repeatability coefficients of 1625.4 PU for ACh, and 386.0 PU for ET-1 (95% CI: ACh, -1438 to 1747 PU, ET-1, -399 to 358 PU) and between observers with repeatability coefficients of 1057.2 PU for ACh and 255.8 PU for ET-1 (95% CI: ACh, -1024 to 1048 PU, ET-1, -252 to 249 PU). The variability between these responses was independent of average flux values for both ACh and ET-1. There was a significant correlation between responses measured in the same site, in the same individual on two different days by the same observer (ACh, r = 0.94, P < 0.0001; ET-1, r = 0.90, P < 0.0006), and between responses measured by two different observers (ACh, r = 0.94, P < 0.0001; ET-1, r = 0.91, P < 0.0003).A. M. Opazo Saez et al. 51259 :5 Br J Clin Pharmacol

Assessing endothelial dysfunction in adolescents and young adults with type 1 diabetes mellitus using a non-invasive heat stimulus

“…Multiple linear regression models were constructed to explore the independent determinants of the major outcomes: percent change in perfusion units from baseline to heating and percent change in area under the curve from baseline to heating. The use of the area under the curve in the assessment of skin microvascular reactivity using laser Doppler flow is well-validated, because it represents the overall flux response to different physiological and pharmacological stimuli (23)(24)(25)(26). Initial models for percent change in perfusion units or percent change in area under the curve included T1D group and were adjusted for skin temperature differences between groups and either baseline perfusion units or baseline area under the curve, respectively.…”

Low local blood perfusion, high white blood cell and high platelet count are associated with primary tumor growth and lung metastasis in a 4T1 mouse breast cancer metastasis model

“…Erythrocytes reflect the laser beam, which enables the recording of the returning signal using a detector positioned in the scanner head. The returning signal is converted to an electrical signal, which is proportional to tissue perfusion (22). The underlying perfusion intensity values are expressed according to the diVerent color scale (23), extending from blue (low perfusion values) over green and yellow to red (highest perfusion values).…”

The role of nitric oxide‐ and prostacyclin‐independent vasodilatation in the human cutaneous microcirculation: effect of cytochrome P450 2C9 inhibition

“…In pilot experiments, we assessed responses at different times and also found no differences but due to a single application of sulfaphenazole the problem could not be entirely overcome. On the other hand, the advantage of the microinjection method over some other methods is that it enables topical application of minimum quantity of vasoactive drug directly to the microcirculation with negligible systemic effects and as such excludes a possible effect of the drug to conductive vessels that may be different from the effect on microvessels and may interfere with the microvessel-effect (Wenzel, 1997;Binggeli et al, 2003;Leslie et al, 2003;Opazo Saez et al, 2005;Gaubert et al, 2007).…”

“…To investigate whether EDHF is a CYP 2C9 metabolite in human skin, we used a specific CYP 2C9 inhibitor, sulfaphenazole. Drugs (L-NMMA, diclofenac and sulfaphenazole) were applied by an intradermal microinjection, described elsewhere (Wenzel, 1997;Leslie et al, 2003;Opazo Saez et al, 2005;Lenasi & Strucl, 2008); saline was injected as a control. 10 ll of solution was injected into the forearm skin through 50-ll-graduated needles (30G; Hamilton, Bonaduz, Schweiz).…”