PubMedDate not supplied
The effects of different concentrations of an extract of Ginkgo biloba (Gb) and of chlorpromazine (CPZ) on the osmotic lysis of rat erythrocytes (produced by dilution of the incubation medium by 30%-70%) were compared in vitro. The erythrocytes were incubated together with Gb or Cpz at the time of the hemolytic reaction at 25 degrees or 37 degrees C in either a simple phosphate buffer or in a more complete buffer containing inorganic salts at physiological concentrations. CPZ produced a dose-dependent increase in the membrane resistance, the maximum effect occurring at 10(-4) M regardless of the experimental conditions used. Gb also increased membrane resistance, but to a lesser extent than CPZ. In addition, Gb was more effective under conditions which increased erythrocyte membrane fragility; i.e., 37 degrees C, simple phosphate buffer. The mechanism of action of Gb seems to differ from that of CPZ. The activity of CPZ (as a membrane stabilizer) is, in part, due to its penetration into the membrane phospholipid layer. Gb might act in a similar manner, but could also modify Na+ transport across the cell membrane by an action on adrenergic receptors, or could stimulate Na+, K+-ATP-ase activity, as has been described for norepinephrine. As Gb contains many molecular constituents: its action on the membrane is likely to be quite complex; but this effect could be associate with its vascular therapeutic action.