Expression of functionally active cannabinoid receptor CB1 in the human prostate gland

Cannabinoids exert a wide spectrum of effects in men including alterations in the reproductive system. To date, two types of cannabinoid receptors have been cloned in humans, namely CB(1) and CB(2) belonging to the G protein-coupled receptor superfamily. Although cannabinoids have functional and morphologic effects in the prostate gland, the expression of cannabinoid receptors in this tissue has never been investigated. The aim of this study was to analyze the expression of cannabinoid receptors in the human prostate gland and their regulatory effects on adenylyl cyclase activity.

To investigate the existence of cannabinoid receptors in prostate, we used various methods, including reverse transcriptase-polymerase chain reaction, Western blotting, and immunohistochemistry. Adenylyl cyclase activity was analyzed by measuring the cAMP produced by means of a competitive assay by using PKA.

Both mRNA for CB(1) and the corresponding protein are expressed in the human prostate gland at a level comparable with the receptor expressed in cerebellum. The molecular mass of the protein estimated from Western blot analysis was 58 kDa, which is in concordance with previous data for CB(1) in other tissues. Immunohistochemical studies show that CB(1) is preferentially expressed in the epithelia of the prostate. The cannabinoid receptor expressed in the prostate negatively regulates adenylyl cyclase activity through a pertussis toxin-sensitive protein.