| Abstract: |
Opioid receptors are widely expressed in the central nervous system where they mediate the analgesic actions of opioids and modulate numerous endogenous functions. However, evidence has been accumulating for perpipheral actions as well. Opioids have been implicated in the regulation of tumor growth and biology. Growth-inhibitory effects of opioids have already been reported form in vivo and in vitro studies of diverse tumors types. Lung opioid receptors also have been suggested (for review, see Life Sci. 66:2221, 2000), perhaps explaining the utility of nebulized morphine for dyspnea. Our previous studies have identified at least sixteen alternatively spliced variants of the mouse mu opioid receptor gene, mainly from the central nervous system. We also isolated three splice variants, mMOR-1C, mMOR-1G and mMOR-1K, as well as the original MOR-1 from lung. In the current studies, we report the identification of three additional variants, mMOR-1D, mMOR-1H and mMOR-1J, in lung by using a RT-PCR approach. Sequence analysis indicated that these variants were identical to those previously reported in mouse brain. Expression of the variant was examined by Northern blot analysis with the exon-specific probes and Western blot with an antisera raised against a exon 11-specific sequence. Furthermore, immunohistochemical studies with the mMOR-1C antisera showed MOR-1C-like immunoreactivity in at least two types of cells in lung. Further characterization of these variants will provide insights of the functional significance of the variants in lung. |
