Objective: To further investigate the action mechanisms of berberine (Ber), and assess the effects of Ber on the in vitro formation of cGMP and cAMP in the isolated rabbit corpus cavernosum.
Methods: Isolated segments of the rabbit corpus cavernosum were exposed to different concentrations of Ber, and, the dosage-dependent accumulations of cGMP and cAMP were determined in the tissue samples by means of 125I radioimmunoassay. Responses of the isolated tissue preparations to Ber were compared with those obtained with the reference compound sildenafil (Sil).
Results: Ber increased cGMP concentrations directly (P < 0.05). In the presence of sodium nitroprusside (SNP), a stimulatory agent of cGMP, both Ber and Sil increased cGMP with increasing dosage (P < 0.01), the EC, values being 1.32 and 0.67 micromol/L respectively. With the same concentration, neither Ber nor Sil influenced the cAMP level significantly (P > 0.05). In the presence of PGE1, a stimulator of cAMP, Ber and Sil also raised the cAMP level concentration (P < 0.01 ), the EC, values being 4.90 (Ber) and 6.53 (Sil) micromol/L respectively.
Conclusion: Ber can increase cGMP and cAMP concentrations in the corpus cavernosum smooth muscles, which may contribute to its action of relaxing corpus cavernosum smooth muscles.