Characterization of muscarinic cholinoceptor in primary culture of smooth muscle cells from human prostate.

We obtained a primary culture of prostatic cells by an explant method from patients with benign prostatic hypertrophy (BPH). Ultrastructural morphology and growth characteristics of these cells conformed to those reported for smooth muscle cells isolated from vascular and visceral tissue sources. The cells retained their original character including the presence of androgen receptor, acid phosphatase and normal chromosomal number. [3H]-methyl-quinuclidinyl benzilate (QNB) saturation experiments showed the existence of a homogeneous population of binding sites with a high affinity and low capacity (KD = 0.17 +/- 0.05 nM., Bmax = 15,000 sites per cell). Inhibition of [3H]-methyl-QNB binding by nonlabelled compounds showed these [3H]-methyl-QNB binding sites to be M2 muscarinic cholinoceptors. cAMP formation induced by forskolin and isoproterenol was inhibited by carbamoyl choline and oxotremorine. These results suggest that prostatic smooth muscle cells contain M2 muscarinic cholinoceptors and that these cholinoceptors couple adenylate cyclase inhibition.