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Serotonin receptors in rat lung
Respiration; International Review of Thoracic Diseases
|January 1, 1986
Summary
Mammalian lungs actively inactivate serotonin and contain multiple serotonin receptors. These receptors, found in mitochondrial and microsomal fractions, may explain known and unknown lung actions of serotonin.
Area of Science:
- Pulmonary Pharmacology
- Molecular Biology
- Biochemistry
Background:
- Mammalian lungs are known to store and inactivate serotonin via active uptake and metabolism.
- Serotonin exhibits direct effects on lung tissues, including smooth muscle constriction, suggesting the presence of specific receptors.
Purpose of the Study:
- To identify and characterize serotonin binding receptors within the rat lung.
- To investigate the affinity and capacity of these receptors in different lung fractions.
Main Methods:
- Purification of mitochondrial and microsomal fractions from rat lung.
- Radio-ligand binding assays using (3H)-serotonin to determine binding kinetics.
- Saturation analysis to calculate dissociation constants and maximum binding capacities.
Main Results:
- Identification of multiple serotonin binding sites in rat lung.
- Outer mitochondrial membranes showed a high-affinity, high-capacity binding site (Kd = 8.3 nM, Bmax = 0.819 pmol/mg).
- Inner mitochondrial membranes exhibited a low-affinity, low-capacity site (Kd = 25.2 nM, Bmax = 0.453 pmol/mg), and microsomal fractions displayed a moderate-affinity, high-capacity site (Kd = 14.8 nM, Bmax = 0.760 pmol/mg).
Conclusions:
- The rat lung possesses distinct serotonin receptors in mitochondrial and microsomal fractions.
- These receptors contribute to the lung's role in serotonin inactivation and may mediate known and novel serotonin actions within the pulmonary system.