Journal of Physiology (1996), 494.1, pp. 307-313

The effect of acetylchlorine on finger capillary pressure and capillary flow in healthy volunteers

S. J. Morris, S. Kunzek and A. C. Shore

Department of Vascular Medicine, Diabetes Research, Postgraduate Medical School, University of Exeter, Barrack Road, Exeter EX2 5AX, UK

1. Consitutive nitric oxide (NO) synthase has been demonstrated in human skin microvascular endothelial cells; however, the physiological significance of this finding is not known. The aim of this study was to investifate the effects of accethylcholine (ACh), which stimulates the release of NO from endothelial Cells, on skin capilary pressure, capillary pulse pressure amplitude (CPPA) and capillary red blood cell velocity (CBV) in healthy volunteers.

2. Finger nailfood capillary pressure was measured in five healthy volunteers. CBV was measured in capillaries of the dorsal middle phalangeal area of the finger in six subjects using a recently developed capillary anemometer. In each case the responses to iontophoretically applied ACh and vehicle were measured on two seperate finbgers on the left hand.

3. Application of vehicle did not significantly change either capillary pressure, CPPA or CBV. ACh significantly increased capillary pressure (from 15.8 ± 2.2 mmHg under basal conditions to 27.7 ± 3.8 mmHg at the plateau of the ACh response; P < 0.008), CPPA (from 2.4 ± 0.22 mmHg at baseline to 8.4 ± 2.4 mmHg at the plateau of the drug response; P < 0.013) and CBV (from 0.54 ± 0.22 mm/s at baseline to 2.46 ± 1.12 mm/s after ACh; P < 0.008).

4. The increases in capillary pressure, CPPA and CBV following the application of ACh suggest that the overall effect of ACh was to induce a reduction in the pre- to postcapillary resistance ratio.

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