μ3 Opiate receptor expression in lung and lung carcinoma: ligand binding and coupling to nitric oxide release

The mu 3 opiate receptor subtype is expressed in human surgical specimens of both normal lung and non-small-cell lung carcinoma. Nitric oxide (NO) release is mediated through the mu 3 receptor, and in lung carcinoma, morphine-stimulated NO release is significantly higher and prolonged than in normal lung. Using reverse transcriptase-polymerase chain reaction (RT-PCR) and Southern blot analysis we show that specific mu opioid receptor transcripts are present in lung carcinoma and other cells with the mu 3 profile. Our findings identify a unique role for the mu 3 opiate receptor in opiate-mediated NO release and suggest that endogenous opiates, through their release of NO, may play a role in cancer progression

Ascaris suum, an intestinal parasite, produces morphine.

The parasitic worm Ascaris suum contains the opiate alkaloid morphine as determined by HPLC coupled to electrochemical detection and by GC-MS. The level of this material is 1168 ± 278 ng/gm worm wet weight. Furthermore, Ascaris maintained for 5 days contained a significant amount of morphine, as did their medium, demonstrating their ability to synthesize the opiate alkaloid. To determine if the morphine was active, we exposed human monocytes to the material and they immediately released nitric oxide in a naloxone-reversible manner. The anatomic distribution of morphine-immunoreactivity reveals the material is in the subcuticle layers and in the animals' nerve chords. Furthermore, as determined by RT-PCR, Ascaris does not express the transcript of the neuronal mu receptor. Failure to demonstrate the expression of this opioid receptor, as well as the morphine-like tissue localization in Ascaris, suggests that the endogenous morphine is intended for secretion into the microenvironment