Capillary Permeability

Mian and coworkers (1977) proposed that anthocyanins protected blood vessels by stabilizing membrane phospholipids and by increasing production of the acid mucopolysaccharides of the connective ground substance. Anthocyanin extracts inhibited porcine elastase in vitro (Jonadet et al., 1983). Vascular protection in rats was measured by retention of Evans blue dye in serum, and appeared to be dose-dependent. Grape (Vitis vinifera) anthocyanins were better at protecting blood vessels than V. myrtillus extracts at the lowest dose, 50 mg/kg/I.P. Extracts from both fruits were significantly different from the control treatment at doses of 100 and 200 mg/kg/I.P.

Capillary strength is another important element in cardiovascular health. Easily damaged or porous capillaries contribute to electrolyte imbalances, and lead to edema and other dysfunctions. The commercial V myrtillus preparation Difrarel® containing 20 mg of anthocyanins was tolerated well by patients with chronic illnesses affecting blood vessels, even though patient improvement was mixed (Amouretti, 1972). Coget and coworkers (1968) described the progress of 27 patients treated with Difrarel 20®, and concluded that the drug was an effective vascular protective agent. Exposure to radiation, either therapeutic or accidental, promotes weakened capillaries. Interest in protective effects of V. myrtillus against radiation damage has been high in Eastern Europe.

Oral doses of V. myrtillus extract were slightly less effective in increasing capillary resistance to permeability than were intraperitoneal administrations to rabbits and rats (Lietti et al., 1976a). However, hamsters given oral doses (10 mg/10 g body weight) of a commercial product containing 36% bilberry anthocyanosides for 2 or 4 weeks exhibited better capillary perfusion and fewer sticking leukocytes in the capillaries that had been clamped to induce ischemia (Bertuglia et al., 1995).

A commercial V. myrtillus extract, known as Myrtocyan®, with 25% anthocyani-dins, was effective in reducing capillary permeability and increasing capillary resistance (Cristoni and Magistretti, 1987). The extract was administered intraperi-toneally to rats starved for 16 hr, then Evans blue dye was given intravenously, followed by an intradermal dose of histamine. Rats given varying amounts of Myrtocyan had reductions of 32-54% in permeability.

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