Dexamethasone therapy selectively increases the sensitivity to noradrenaline of the rat mesenteric circulation.

We studied the effects of dexamethasone on the vascular responsiveness of the isolated perfused mesenteric vascular bed of the rats. Dexamethasone was infused at a low dose (2 micrograms/day) to avoid steroid-induced catabolic effects. The mesenteric arteries were perfused with increasing concentrations of noradrenaline, vasopressin and potassium chloride. Vascular responses to vasopressin and potassium chloride were similar in both dexamethasone-treated and control arteries. However, the dexamethasone treatment increased the sensitivity, but not the maximal pressor response, to noradrenaline. These results show that dexamethasone selectively increases the vascular sensitivity to noradrenaline in rats before the development of systemic hypertension.