A comparison of the binding and functional properties of alpha-1 adrenoceptors and area density of smooth muscle in the human, canine and rat prostates.

The present study was designed to compare the binding and functional properties of alpha-1 adrenoceptors and the area density of smooth muscle in the human, canine and rat prostates. Chloroethylclonidine (CEC)-sensitive and -insensitive alpha-1 adrenoceptors were characterized on slide-mounted prostatic tissue sections using the ligand [3H]prazosin. The mean equilibrium dissociation constants (Kd) for [3H]prazosin binding sites were not significantly different among the three different species. The densities (Bmax) of CEC insensitive [3H]prazosin binding sites in the human, canine and rat prostates were 1.71 +/- 0.32, 0.35 +/- 0.04 and 0.84 +/- 0.11 fmol/mg of wet weight, respectively. The Bmax of CEC-sensitive [3H]prazosin binding sites in the human, canine and rat prostates were 1.32 +/- 0.83, 0.44 +/- 0.11 and 0.25 +/- 0.10 fmol/mg of wet weight, respectively. The contractile response elicited by the rat prostate in the presence of phenylephrine was consistently negligible. The mean maximal force after phenylephrine challenge (phenylephrine Emax) in the human and canine prostates were 0.125 +/- 0.025 g of force/mm2 cross-sectional area and 0.096 +/- 0.014 g of force/mm2 cross-sectional area, respectively. CEC inactivated 80 and 53% of the phenylephrine contractile response in man and dog, respectively. The mean percentage of area densities of smooth muscle in the human, canine and rat prostates were 38.8, 12.9 and < 1%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)