Age-related changes in the vasodilating actions of Ginkgo biloba extract and its main constituent, bilobalide, in rat aorta

Abstract

Background Age-related modulation in vasodilating actions induced by Ginkgo biloba extract (GBE) and bilobalide, a main constituent of GBE, were examined using rat aorta ring strips. Methods Wistar rats from 5 to 25 weeks old were used, and the isolated aorta ring strips were fixed in Krebs–Henseleit solution. Results GBE and bilobalide concentration-dependently dilated norepinephrine (NE)-induced vasoconstriction in all aged rats. The vasodilating actions generally decreased in accordance with aging. GBE at 1 mg/ml decreased from 28.4±3.8% ( n=5) in 5-week-old rats to 23.7±7.1 ( n=7) in 25-week-old rats, but not significantly. GBE (3 mg/ml)-induced vasodilation was maximum by 73.7±2.1% ( n=4, P<0.001) in 10-week-old rats. GBE had the marked vasodilation at younger ages and further decreased it with developing ages. In the rats older than 20 weeks, however, GBE tended to rather increase the strength of vasodilating action. On the other hand, the vasorelaxation induced by 30 μmol/l bilobalide significantly decreased from 11.8±1.4% ( n=4) in 5-week-old rats to 2.3±1.5% ( n=5, P<0.01) in 25-week-old rats, and by 100 μmol/l from 20.2±3.4% ( n=4) to 5.6±2.5% ( n=5, P<0.01), respectively. Bilobalide had the similar age-related actions. The age-dependent attenuation was produced milder by bilobalide than by GBE. At lower concentrations, however, bilobalide caused the weak vasocontriction in 20- and 25-week-old rats. Conclusion GBE and bilobalide possess a similar characteristic for age-related modification, clinically suggesting the more effective actions of GBE for elder persons.