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Met5-enkephalin-arg6-phe7 and its receptor in lung
Abstract:
The presence of met5-enkephalin-arg6-phe7 (YGGFMRF) and opiate receptors in rat, guinea pig and human lung was investigated with specific and sensitive radio immuno- and radio-receptor assays. 1) High and low molecular weight YGGFMRF-like immunoreactivity were detected in lung extracts using Bio-Gel P-2 column chromatography followed by radioimmunoassay. Using HPLC, we determined that the low molecular weight YGGFMRF-like immunoreactivity is authentic YGGFMRF. 2) The contents of YGGFMRF were 0.68 +/- 0.08, 0.76 +/- 0.12 and 0.63 pmol/mg protein in lung of rat, guinea pig and human, respectively. In the lung of these three species, the content of YGGFMRF is much greater than that of met5-enkephalin. 3) 47 mM KCl released YGGFMRF from rat lung slices in a Ca++ dependent manner. 4) Rat lung membranes were shown to bind [3H]-etorphine in a saturable manner. There are two populations of binding sites with a Kd = 0.6 and 7.1 nM and a Bmax = 7.8 and 28.5 fmol/mg protein, respectively. This binding could be displaced by YGGFMRF with high affinity, the other endogenous opioid peptides were poor displacers. From these results, we infer that YGGFMRF might be a putative neurotransmitter or neuromodulator, its role in the regulation of lung function can now be investigated.
Insights
Met5-enkephalin-Arg6-Phe7 (YGGFMRF) and opiate receptors are present in mammalian lungs. YGGFMRF is identified in rat, guinea pig, and human lung tissue, suggesting a potential role in lung function regulation.
Area of Science:
- Pharmacology
- Neuroscience
- Respiratory Physiology
Background:
- The presence and function of endogenous opioid peptides and their receptors in the lung are not fully understood.
- Met5-enkephalin-Arg6-Phe7 (YGGFMRF) is an opioid peptide with potential biological activity.
Purpose of the Study:
- To investigate the presence and characteristics of YGGFMRF and opiate receptors in rat, guinea pig, and human lung tissue.
- To explore the potential role of YGGFMRF in lung function.
Main Methods:
- Radioimmunoassay and radio-receptor assays were employed to detect and quantify YGGFMRF and opiate receptors.
- High-performance liquid chromatography (HPLC) was used to confirm the identity of YGGFMRF.
- KCl-stimulated release and [3H]-etorphine binding assays were performed on rat lung membranes.
Main Results:
- Authentic YGGFMRF was detected in rat, guinea pig, and human lung extracts at concentrations significantly higher than met5-enkephalin.
- YGGFMRF release from rat lung slices was calcium-dependent.
- Rat lung membranes exhibited saturable binding of [3H]-etorphine, with YGGFMRF showing high-affinity displacement.
Conclusions:
- YGGFMRF is present in mammalian lungs and binds to opiate receptors.
- YGGFMRF may function as a neurotransmitter or neuromodulator in the lung.
- Further research is warranted to elucidate the specific role of YGGFMRF in regulating lung function.