Showing papers by "Andreas Pfeiffer published in 1988"
TL;DR: Data show that muscarinic M2 binding sites in mucosa and smooth muscle can be distinguished by both agonist and antagonist binding experiments, and suggest the existence of different subtypes of M2-binding sites in these tissues.
31 citations
TL;DR: The muscarinic agonists oxotremorine, pilocarpine, and bethanechol elicited partial increases in inositol phosphates at maximal drug concentrations, and these partial increases correlated with their ability to stimulate [14C]aminopyrine uptake, indicating that inositl polyphosphates may be a second messenger of M2 receptors stimulating acid secretion.
Abstract: The muscarinic receptor system involved in hydrogen ion production by enriched rat gastric parietal cells was investigated Muscarinic receptor density determined by [N-methyl-3H]scopolamine binding was 8,100/cell The receptor appeared to be of the M2 muscarinic receptor subtype, since it had a low affinity (Kd, 189 nM) for the M1 receptor antagonist pirenzepine compared with atropine (Kd, 074 nM) Receptor activation by carbachol rapidly augmented levels of polyphosphoinositides, indicating an activation of a phospholipase C The dose-response relations for the increase in inositol phosphates closely paralleled the binding of carbachol to muscarinic receptors with a Km of 17 microM The inositol phosphate response was antagonized by pirenzepine with a Ki of 177 nM The stimulation of inositol phosphate levels by carbachol correlated well with the stimulation of [14C]aminopyrine uptake, determined as an index of acid secretion The muscarinic agonists oxotremorine, pilocarpine, and bethanechol elicited partial increases in inositol phosphates at maximal drug concentrations, and these partial increases correlated with their ability to stimulate [14C]aminopyrine uptake These data indicate that inositol polyphosphates may be a second messenger of M2 receptors stimulating acid secretion
20 citations
1 citations