Skin Blood Flow Responses and Forearm Reactive Hyperemia After Niacin Ingestion.

Skin blood flow and core temperature were measured before and after niacin ingestion in eight subjects. Each subject was tested on two occasions in climatic conditions of 30 deg C with moderate humidity. Following niacin ingestion, peak forearm blood flow FBF by venous occlusion plethysmography averaged 8.01.7 ml100mlmin from an average baseline of 2.20.5 ml100mlmin, an increase of 265. Forearm skin blood flow laser doppler flowmetry, LDF increased 310 83 at peak niacin vasodilation to 13.1 4.1 ml100mlmin from the baseline of 3.4 1.4 ml100mlmin. Chest skin blood flow LDF increased 550 154 compared to baseline. Higher skin blood flow significantly increased heat loss from the skin decreasing core temperature an average of 0.44 deg C 0.10 after niacin ingestion. Reactive hyperemia measured by laser doppler flowmetry in forearm skin upon the release of brachial arterial occlusion averaged 11.9 1.7 ml100mlmin, an increase of 250110 above control blood flow. This hyperemic response was 12 less than peak skin blood flow observed during the maximal niacin effect. Nicotinic acid, increased skin blood flow, increased skin temperature and decreased core temperature as we reported previously. Although widespread skin vasodilation occurred in most subjects, the extent of the vasodilation and the intensity of subjective symptoms varied within and between individuals.