Selective and sustained occupancy of prostatic α1-adrenoceptors by oral administration of KMD-3213 and its plasma concentration in rats

Abstract

Abstract This study examined the ex-vivo occupancy by KMD-3213 of α1-adrenoceptors in the prostate and other tissues of rats in terms of tissue selectivity and duration of occupancy in relation to plasma concentration. Oral administration of KMD-3213 (0.2–20.2μmol kg−1, 0.5 h) dose-dependently decreased [3H]prazosin binding sites (Bmax) in the prostate (42–74%) and submaxillary gland (54–88%) compared with the control value. In contrast, there was only a slight change in the Bmax values in the spleen and cerebral cortex of KMD-3213-treatedrats. The α1-adrenoceptor occupancy in the prostate and submaxillary gland was increased, with plasma free concentration of KMD-3213 at 0.5 h after oral administration of KMD-3213 (0.6–20.2 μ mol kg−1). The receptor occupancy in these tissues was much greater than that in the spleen, heart or cerebral cortex. After oral administration of KMD-3213 (6.1 μ mol kg−1), the α1-adrenoceptor occupancy in the prostate and submaxillary gland occurred rapidly, in parallel with the rise in the plasma concentration of the drug, and it lasted for at least 24 h, despite a remarkable decrease in the plasma concentration. It is concluded that KMD-3213 may produce fairly selective and sustained occupancy of α1-adrenoceptors in the prostate, a target organ for treatment of bladder outlet obstruction in patients with benign prostatic hyperplasia.