Inhibitory effect of the flavonoid O-(beta-hydroxyethyl)-rutoside on increased microvascular permeability induced by various agents in rat skin.

Flavonoids are used clinically in conditions with inflammatory oedema. The effects of a clinically employed flavonoid preparation, O-(beta-hydroxyethyl)-rutoside, in this paper abbreviated 'HR', were studied in a rat skin model designed to evaluate the leakage of 125I-labelled human serum albumin after intracutaneous injection of substances increasing microvascular permeability. Intravenous injection of 25-500 mg HR/kg body weight (b.w.) 30 min before administration of permeability-increasing agents gave a dose-related attenuation of the permeability increase due to histamine, bradykinin and fibrin degradation products. The maximum inhibitory effect of HR was observed at 250 mg/kg b.w.. Treatment with the beta 2-receptor agonist terbutaline also reduced the increased permeability. This effect of HR and terbutaline included reduction of oedema due to formaldehyde, citrate and dextran 70. The effect of terbutaline was counteracted by the beta-receptor blocker propanolol. The effect of HR on blood flow in the skin, determined as clearance of 133Xe, was not considered important as an explanation for its inhibition of microvascular permeability.