Muscarinic stimulation of submucosal glands in swine trachea.
The properties of muscarinic acetylcholine receptors (mAChR) on tracheal explants and isolated submucosal gland cells were determined using [3H]quinuclidinyl benzilate ([3H]QNB) and N-[3H]methylscopolamine ([3H]NMS) as ligands. Analysis of competitive displacement of ([3H]NMS binding by pirenzepine demonstrated the presence of M1- (27 +/- 2%) and M2G- (73 +/- 2%) receptors on isolated tracheal submucosal gland cells (TSGC's) in control. Daily administration of diisopropylfluorophosphate (DFP) inhibited cholinesterase activity by greater than 95%. After 7 days of DFP treatment, [3H]QNB binding to intact TSGC's decreased from 14.2 +/- 0.6 to 6.3 +/- 0.8 fmol/10(6) cells; similarly, [3H]NMS binding fell from 8.1 +/- 1.9 to 2.0 +/- 0.8 fmol/10(6) cells. The loss of mAChR's was predominantly of the M2G subtype with the relative proportion dropping to 33%. In addition, 90% of the receptors assumed the high-affinity state for carbachol displacement of [3H]NMS. Mucus secretion was quantitated by measuring the release of 3H-labeled mucus macromolecules from explants of tracheal submucosal glands and isolated cells. Acetylcholine (ACh), 2 X 10(-5) M, stimulated mucus secretion by 2.5 and 2.3 times the basal rate, respectively. Elimination of acetylcholinesterase (AChe) by DFP increased the ACh sensitivity by 18- and 5-fold. Tracheal explants or TSGC's obtained 2 h after an in vivo DFP treatment showed a 6- and 3-fold ACh stimulation. This ACh sensitivity decreased during the continued daily dosing with DFP such that only a 1.3- and 1.1-fold ACh stimulation was apparent after 7 days of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
Yang
C M
CM
Department of Pharmacology, University of Mississippi Medical Center, Jackson 39216-4505.
Farley
J M
JM
Dwyer
T M
TM
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001667:Binding, Competitive; D002217:Carbachol / Q000494:pharmacology; D005088:Exocrine Glands / Q000166:cytology / Q000378:metabolism*; D007531:Isoflurophate / Q000494:pharmacology*; D008297:Male; D009093:Mucus / Q000378:metabolism*; D019832:N-Methylscopolamine; D010890:Pirenzepine / Q000494:pharmacology; D011813:Quinuclidinyl Benzilate / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000187:drug effects*; D012602:Scopolamine Derivatives / Q000378:metabolism; D013552:Swine; D014132:Trachea / Q000187:drug effects* / Q000378:metabolism
D011976:Receptors, Muscarinic; D012602:Scopolamine Derivatives; D007531:Isoflurophate; D010890:Pirenzepine; D011813:Quinuclidinyl Benzilate; D001285:Atropine; D002217:Carbachol; D019832:N-Methylscopolamine