1. Reactivity to noradrenaline was measured in resistance vessels of isolated perfused rat tails in two experiments. In the first experiment the three treatment groups were ‘desoxycorticosterone (DOCA)/saline/nephrectomy’, ‘saline/nephrectomy’ and ‘intact/water’. In the second experiment an additional‘nephrectomy/water’ group was included and reactivity to vasopressin was also measured.
2. DOCA/saline/nephrectomy animals were hypertensive for at least 4 weeks before they were killed.
3. Vascular reactivity to noradrenaline was increased in preparations from DOCA/saline/nephrectomy and saline/nephrectomy groups compared with the intact/H2O group in both experiments. This increased reactivity was not associated with an elevated baseline vascular resistance.
4. In contrast to noradrenaline, responses to vasopressin did not differ significantly between the groups.
5. These results support the theory that the effects of sodium balance on arterial pressure are mediated at least in part by changes in resistance vessel reactivity to noradrenaline.