(+)-Cyanidanol-3 as inhibitor of prostaglandin synthetase. Studies on renal medulla and liver of the rat in vitro and in vivo.

(+)-Cyanidanol-3 inhibits the prostaglandin synthetase of the renal medulla and of the liver of rats in vitro and after treatment of the animals with 200 mg/kg. A half-maximal inhibition of the enzyme was obtained with 5 . 10(-5) M cyanidanol. If the microsomal inhibitor CFT1201 is first applied, the inhibitory effect in vivo of 50% is increased to 80%. It is supposed that cyanidanol is converted to metabolites which, according to our earlier studies, activate the enzyme system. An enzyme activity of the rat liver was measured which - with a turnover of 18-20% - was significantly higher than the values obtained by other authors.