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

The μ3 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 μ3 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 μ opioid receptor transcripts are present in lung carcinoma and other cells with the μ3 profile. Our findings identify a unique role for the μ3 opiate receptor in opiate-mediated NO release and suggest that endogenous opiates, through their release of NO, may play a role in cancer progression.