Inhibitory effect of buflomedil on prostate α_1A adrenoceptor in the Wistar rat

The inhibitory effect of buflomedil on α_1A-adrenoceptor (AR) in the prostate of Wistar rat was investigated in this study. Normotensive and spontaneous hypertensive rats were orally fed with buflomedil (150 mg/kg). The drug effects on blood pressure and heart rate were monitored by photoelectric volume oscillometric method. Prostate tissue strips from normotensive rats were contracted in vitro in organ bath by phenylephrine (10^-8 to 10^-2 M). The inhibitory effects of buflomedil (10^-9 to 10^-7 M) on the phenylephrine-induced contractions were measured. Radioligand binding displacement study by buflomedil was performed on rat prostate α_1A-adrenoceptor (AR) and spleen α_1B-AR. Furthermore the effects of buflomedil and WB-4101 on phenylephrine (10 μM) activated uptake of 2-[¹⁴C]-deoxy-D-glucose (2-DG) into C₂C₁₂ cells were evaluated. The results showed that buflomedil feeding did not alter the systolic blood pressure of either spontaneous hypertensive rats or normal rats. Dose-inhibition curves of phenylephrine-induced prostate contraction demonstrated a higher potency of buflomedil than tamsulosin. Buflomedil displaced [³H]prazosin binding in a concentration-dependent manner both in rat prostate α_1A- AR and spleen α_1B-AR. The ratio of affinity to α_1A-AR and α_1B-AR for buflomedil was 4.06/6.84, indicating selectivity on α_1A-AR over α_1B-AR. Activation of C₂C₁₂ cell α_1A-AR by phenylephrine increased the glucose uptake to 116%. Both buflomedil and WB-4101 inhibited the uptake in a concentration-dependent manner. In conclusion, the findings showed that buflomedil has preferential α_1A-AR antagonistic effect to inhibit prostate contraction without significantly affecting the blood pressure.