RESUMO
Experiments were carried out on isolated rabbit hearts: PG biosynthesis was induced by administration into the coronary circulation of a single dose of arachidonic acid (100 micrograms) and the PGs synthesized and released in the heart effluent were detected by bioassays. Total flavonoids (TF) extracted from Ribes nigrum leaves and their 2 major components, rutin and isoquercitrin had neither spasmodic nor relaxing activity on rat stomach strip. They were not capable of inducing any biosynthesis and release of PG-like substances and did not act on PGE2 receptors. They inhibited both biosynthesis and release of PG-like substances: TF were more active than rutin and isoquercitrin: ID30 was 1.03 +/- 0.24 mg/ml for TF versus 3.75 +/- 0.24 mg/ml and 2.31 +/- 1.4 mg/ml for rutin and isoquercitrin respectively.