Strips of digital arteries obtained post-mortem from thirteen hypertensives have been compared with those from thirteen normotensives. 2. The strips from hypertensives and from males had a significantly greater response to 80 mmol/l KCl, but this was due to the increased cross-sectional areas of the strips from hypertensives and from males. 3. The maximum responses to noradrenaline and serotonin, but not the pED50 values, were significantly smaller in the strips from the hypertensives than in those from the normotensives, but there were no differences between the strips from hypertensives and normotensives in either the maximum response or pED50 values to angiotensin or barium chloride. 4. it is concluded that these results suggest a decreased number of alpha-receptors are present in human hypertensive vascular smooth muscle and this is a sequel either of the increased pressure itself, or of increased exposure in vivo of the blood vessels from hypertensives to noradrenaline.
