Structural changes in alpha1-adrenoceptor antagonist-treated human prostatic stroma.

Alpha1-adrenoceptor antagonists (alpha1-blockers) are currently used as first-line drugs for the treatment of benign prostatic hyperplasia (BPH). However, cases of BPH are often encountered in which the efficacy of alpha1-blockers decreases and switching to surgical treatment is required. One factor responsible for this resistance includes structural changes in prostatic tissue architecture following repeated oral administration of alpha1-blockers. Forty patients suspected of having prostate cancer, but without evidence of malignancy on prostatic biopsy were divided into two groups: an untreated group (n = 17) and an oral alpha1-blocker-treated group (n = 23). Twenty-one patients exhibiting resistance to oral alpha1-blocker therapy who underwent surgery were assigned into the surgically treated group. Each tissue sample was subjected to Masson's trichrome staining to distinguish collagen fibers from smooth muscle constituting prostatic stroma. The mean collagen fiber share was 62.2 +/- 10.4% in the untreated group, 72.1 +/- 9.1% in the oral alpha1-blocker-treated group, and 72.2 +/- 15.7% in the surgically treated group. Focusing on cases exhibiting high-collagen fiber share (70% or more), the distribution in each of the two alpha1-blocker-treated groups (16 of the 23 cases from the oral alpha1-blocker-treated group and 10 of the 21 cases from the surgically treated group) differed significantly from that in the untreated group (2 of the 17 cases). Our findings suggest that the accumulation of collagen fibers in prostatic stroma could be one of the factors responsible for alpha1-blocker treatment.