Quantitative autoradiography of alpha 1 adrenoceptors with [3H]tamsulosin in human hypertrophied prostate using computerized image analysis.

Fourteen specimens of human hypertrophied prostate were evaluated for the distribution of alpha 1 adrenoceptors using autoradiography with a computerized image analysis system. The hypertrophied prostatic specimens, obtained at open prostatectomy, were dissected vertically to the urethra, and sectioned at 10 microns. They were immersed in 1 nM of specific alpha 1 ligand, [3H]tamsulosin chloride ([3H]tamsulosin) and exposed to autoradiographic film. The images were analysed by a computerized image analysis system. The total binding of [3H]tamsulosin in the whole section (n = 14) was 0.82 +/- 0.21 (mean +/- SE) nCi mg-1. The autographic data were correlated with data obtained in a membrane-binding assay. The prostatic tissue studied was divided into urethral, glandular and stromal zones, the latter two zones being further divided into the inner and outer areas. The total binding of [3H]tamsulosin in the urethral zone (n = 7) was 0.65 +/- 0.32 nCi mg-1. The glandular zone contained significantly more abundant alpha 1 adrenoceptors than the stromal zone and their densities (glandular vs stromal) were 1.15 +/- 0.19 nCi mg-1 (n = 14) vs 0.72 +/- 0.15 nCi mg-1 (n = 14), respectively (p < 0.05). The data from the whole section were not affected by prostatic weight. This method described enabled the distribution of the receptors in different sites to be evaluated both morphologically and quantitatively.