[The role of muscarinic receptor subtypes in feline tracheal submucosal gland secretion].

To determine what muscarinic receptor subtype regulates the rise of intracellular calcium concentration ([Ca2+]i) and resultant airway submucosal gland secretion on muscarinic receptor stimulation, we examined the effects of atropine (ART), pirenzepine (PZ), 11([2-(diethylamino) methyl-1-piperidinyl] acetyl)-5,11-dihydro-6H-pirido (2,3-b)(1,4)-benzodiazepine-6-one (AF-DX116) and 4-diphenylacetoxy-N-methylpiperidine methiodode (4-DAMP) on methacholine (MCh)-evoked [Ca2+]i rise in acinar cells, mucus glycoprotein (MGP) secretion and electrolyte secretion from submucosal glands isolated from feline tracheae. [Ca2+]i was measured with the Ca(2+)-sensitive fluorescent dye, fura2. We determined MGP secretion by measuring trichloroacetic acid (TCA)-precipitable 3H-labeled glycoconjugates and electrolyte secretion by the change in the rate constant of 22Na-efflux from isolated glands. Half maximal inhibitory concentrations (IC50) of PZ, AF-DX116, 4-DAMP and ATR against MCh (10(-5) M)-evoked [Ca2+]i rise were 10(-7) M, 6 x 10(-6) M, 8 x 10(-9) M and 6 x 10(-9) M, respectively. IC50 values of these antagonists against MCh (10(-5) M)-evoked MGP secretion were 10(-6) M, 2 x 10(-5) M, 8 x 10(-9) M and 6 x 10(-9) M, respectively. MCh (10(-5) M)-evoked 22Na-efflux was significantly inhibited by 10(-7) M 4-DAMP and 10(-7) M ATR (p < 0.01, respectively), but the inhibitory effect of PZ (10(-7) M) was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)