Rat lung cholinergic receptor: characterization and regulation by corticosteroids.
Muscarinic cholinergic receptors have been implicated in the regulation of bronchomotor tone, bronchial mucus secretion, and lung mast-cell mediator release. Rat lung membranes prepared by homogenization, sonication, and sedimentation of 37,000 g in sucrose have been demonstrated to possess muscarinic cholinergic receptors as assessed by radioligand binding employing l-quinuclidinyl[phenyl-4-3H]benzilate ([3H]QNB). QNB binding was saturable, stereoselective, and reversible in the presence of 1 microM atropine. The rat lung muscarinic receptor demonstrated a Kd of 0.268 +/- 0.126 (+/- SD) nM and a density of 35.4 +/- 4.6 fmol/mg protein by Scatchard analysis. The Hill coefficient was 1.015 +/- 0.085, indicating noncooperative binding. Muscarinic cholinergic receptors in the rat lung were equal in number to alpha 1-adrenergic receptors, but beta-adrenergic receptors are 14 times more prevalent as defined by [3H]prazosin and l-[propyl-2, 3-3H]dihydroalprenolol ([3H]DNA) binding. Dexamethasone (140 micrograms) administration in vivo caused an increase in all three receptor types by 24-48 h, suggesting steroids regulate not only the number of beta-receptors but also that of alpha- and cholinergic receptors. These data suggest new avenues by which steroids may regulate lung function.
D000305:Adrenal Cortex Hormones / Q000502:physiology*; D000818:Animals; D001667:Binding, Competitive; D003907:Dexamethasone / Q000494:pharmacology; D004285:Dogs; D006168:Guinea Pigs; D008168:Lung / Q000032:analysis / Q000294:innervation / Q000502:physiology*; D008297:Male; D008566:Membranes / Q000378:metabolism; D011813:Quinuclidinyl Benzilate / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011941:Receptors, Adrenergic / Q000032:analysis / Q000187:drug effects; D011950:Receptors, Cholinergic / Q000032:analysis / Q000187:drug effects / Q000502:physiology*; D011976:Receptors, Muscarinic / Q000502:physiology*
D000305:Adrenal Cortex Hormones; D011941:Receptors, Adrenergic; D011950:Receptors, Cholinergic; D011976:Receptors, Muscarinic; D011813:Quinuclidinyl Benzilate; D003907:Dexamethasone