Abstract
1. Spirally-cut strips from human visceral arteries isolated in vitro were contracted by noradrenaline and this contraction was antagonized by the α-receptor blocking agent, thymoxamine.
2. The cumulative log dose-response curves to noradrenaline in the presence of thymoxamine were moved to the right of and parallel to the curve for noradrenaline alone. The blockade was surmountable and reversible.
3. The quantitative criteria for simple competitive antagonism were satisfied. When log (x - 1) was plotted against pAx the points fitted a straight line with a slope (-n) of 0.91. The pA2 for thymoxamine was 7.54 and the mean value for log K2 was 7.82. These values are in approximate agreement with those previously reported for animal isolated arterial strips.
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Selected References
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