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An experimental study of the effect of ginkgo biloba extract on the human and rabbit corpus cavernosum tissue
Purpose:
To investigate the effect of subfractions of extract from the ginkgo on human and rabbit corpus cavernosal tissue and their possible use for the treatment of impotence.
Materials And Methods:
Among the fractions of ginkgo biloba extract (GBE), nonginkgolide nonflavonoid fraction (NGF) has the most potent relaxing effect on vascular smooth muscle. We subfractionated NGF and speculated that some of the subfractions might have a very potent relaxing effect on corpus cavernosal tissue. Thereafter we have studied their effect on human and rabbit corpus cavernosum using organ bath and electrical field stimulation experiments.
Results:
In the tissue precontracted by norepinephrine (10(-5)M.), corpus cavernosal tissue of human and rabbit showed relaxation in response to subfractions of NGF in a dose-dependent manner. 304U-1 showed the most potent relaxing effect (ED50 = 0.74 mg./ml. in human, ED50 = 0.66 mg./ml. in rabbit). 304U-1 elicits pharmacological actions on corpus cavernosum smooth muscle via the signal transduction pathway whereby relaxation induced by 304U-1 is mediated by intracellular cAMP and perhaps partially by antagonizing of the adrenergic nervous system. A hyperpolarizing effect via potassium channel opening might also be related to this relaxing effect.
Conclusion:
The subfractions of NGF, especially 304U-1, have a relaxing effect on corpus cavernosum tissue. 304U-1, which showed the most potent relaxing effect, can possibly be used as a drug for intracavernosal injection therapy. Considering the fact that the value of ED50 is too high, further fractionation and in vivo study are needed before clinical use in an oral form.