EFFECTS OF HYDROXYETHYLRUTOSIDES ON THE PERMEABILITY OF MICROVESSELS IN THE FROG MESENTERY

1 We have investigated the effects of a standardised mixture of hydrox yethylrutosides (HR, Venoruton), a mixture of five of its main compone nts (M) and each of the five components separately (7-mono-HR, 7,4'-di -HR, 7,3',4'-tri-HR, 5,7,3',4'-tetra-HR and 7,3'4'-tri HQ) upon the pe rmeability of single perfused capillaries and venules in the mesenteri es of pithed frogs. 2 In each experiment, the hydraulic permeability ( L(p)) of a single perfused microvessel and the effective osmotic press ure (sigmaDELTApi) exerted by macromolecules across its walls were est imated by a microcclusion technique, first during control perfusion an d then in the presence of a known concentration of test substance. 3 H R, M and 7,4'-di-HR reduced L(p) in a similar concentration-dependent manner over the range of 1 mug ml-1 to 1 mg ml-1 (maximum reduction wa s to 40% of control L(p) at 1 mg ml-1). At perfusate concentrations gr eater than 1 mg ml-1, these substances reduced L(p) to a lesser extent . While the four other test substances reduced L(p) significantly when their perfusate concentrations equalled or exceeded 100 mug ml-1, the y were all less potent than 7,4'-di-HR. 4 The reduction in L(p) induce d by the mixture of flavonoids was only slightly reversed by subsequen t perfusion with flavonoid-free solutions. 5 When permeability was inc reased by perfusing with protein-free solutions, both HR and 7,4'-di-H R reduced and then reversed the increase in L(p) in a concentration-de pendent manner over the range of 1 mug ml-1 to 100 mug ml-1. None of t he other component flavonoids was effective in restoring L(p) under th ese conditions.