Up-regulation of α1a and α1d-adrenoceptors in the prostate by administration of subtype selective α1-adrenoceptor antagonist tamsulosin in patients with benign prostatic hyperplasia.

PURPOSE

We examined the change in α(1)-adrenoceptor subtype expression in the prostate due to chronic tamsulosin administration in a benign prostatic hyperplasia rat model and in patients.

MATERIALS AND METHODS

We measured α(1)-adrenoceptor subtype expression after tamsulosin administration in the prostate of the benign prostatic hyperplasia rat model using TaqMan® reverse transcriptase-polymerase chain reaction. We also measured expression before and after 12-week tamsulosin treatment in the prostate of patients with benign prostatic hyperplasia. We examined the correlation between the change in α(1)-adrenoceptor expression due to tamsulosin treatment and acute urinary retention during long-term followup.

RESULTS

The expression of α(1a) and α(1d)-adrenoceptors was significantly increased in dose dependent fashion by tamsulosin in the benign prostatic hyperplasia rat model. Median mRNA expression of subtypes α(1a) and α(1d)-adrenoceptors was 1.4 (IQR 0.6, 3.0) and 1.7 × 1,000 copies per 1 ng β-actin (IQR 0.9, 2.4) before treatment, and 6.0 (IQR 2.0, 8.0) and 2.2 × 1,000 copies per 1 ng β-actin (IQR 1.7, 3.6), respectively, after treatment. The expression of α(1a) and α(1d)-adrenoceptors significantly increased after tamsulosin treatment (p <0.01 and <0.05, respectively). This increase was observed in 10 patients in whom acute urinary retention did not develop during long-term followup but not in 4 in whom acute urinary tract retention developed.

CONCLUSIONS

Tamsulosin up-regulated α(1a) and α(1d)-adrenoceptors, suggesting that it has clinical selectivity for α(1a) and α(1d)-adrenoceptors. Up-regulation of α(1)-adrenoceptors subtype expression is considered an adaptive response to chronic tamsulosin administration. The difference in the response to α(1)-adrenoceptors antagonists among patients may contribute to the diversity in the long-term efficiency of α(1)-adrenoceptor antagonists.