Detection of alpha(1)-adrenoceptor subtypes in human hypertrophied prostate by in situ hybridization

Adrenergic stimulation induces contraction of hypertrophied prostatic tissue via the alpha(1) adrenoceptor, and the results of pharmacological studies suggested the existence of adrenoceptor subtypes. Recently three subtypes (alpha(1a), alpha(1b), and alpha(1d)) were cloned. Using probes for these subtypes, we demonstrated their expression in the tissues of ten cases of benign prostatic hypertrophy, using in situ hybridization. To determine the ratio between these subtypes, an RNase protection assay was also performed in three cases. Expression of the alpha(1a) and alpha(1d) adrenoceptors was diffuse in the smooth muscles of the interstitium, but was absent in glandular epithelial cells. On the contrary, the alpha(1b) adrenoceptor was hardly detectable. The RNase protection assay confirmed the absence of the alpha(1b) adrenoceptor, the ratio of alpha(1a) and alpha(1d) being 4:1. These results supported the idea that the differences in prostatic contractile response to several adrenergic drugs are based on the affinities of these drugs for the different subtypes.