Deoxycholic acid conjugates are muscarinic cholinergic receptor antagonists.
In the course of examining the actions of major human bile acids on cholinergic receptors, we discovered that conjugates of lithocholic acid are partial muscarinic agonists. In the present communication, we report that conjugates of deoxycholic acid (DC) act as cholinergic muscarinic receptor antagonists. Chinese hamster ovary (CHO) cells expressing rat M3-muscarinic receptors were used to test bile acids for inhibition of radioligand [N- (3)H-methylscopolamine ((3)H-NMS)] binding; alteration of inositol phosphate (IP) formation; mitogen-activated protein (MAP) kinase phosphorylation and cell toxicity. We observed approximately 18.8, 30.3 and 37.1% inhibition of (3)H-NMS binding with DC and its glycine (DCG) and taurine (DCT) conjugates, respectively (all 100 micromol/l, p < 0.01). DCT and DCG inhibited acetylcholine-induced increases in IP formation and MAP kinase phosphorylation (p44 and p42 ERK). DCG and DCT did not alter trypan blue exclusion or lactate dehydrogenase release from CHO-M3 cells. We observed the following rank order of potency (IC(50) micromol/l) for inhibition of (3)H-NMS by muscarinic antagonists and bile acids: NMS (0.0004) > 4-DAMP (0.009) > atropine (0.012) > DCT (170) > DCG (250). None of the bile acids tested were hydrolyzed by recombinant cholinesterase. At concentrations achieved in human bile, DC derivatives are natural muscarinic antagonists.
Department of Internal Medicine, Division of Gastroenterology and Hepatology, Central Arkansas Veterans Healthcare System and University of Arkansas for Medical Sciences, Little Rock, Ark. 72205-7199, USA. raufmanjeanpierre@uams.edu
Jean-Pierre
JP
Raufman
Ying
Y
Chen
Piotr
P
Zimniak
Kunrong
K
Cheng
D000818:Animals; D001647:Bile Acids and Salts / Q000494:pharmacology; D016466:CHO Cells; D002462:Cell Membrane / Q000187:drug effects; D018679:Cholinergic Agonists / Q000494:pharmacology; D002802:Cholinesterases / Q000737:chemistry; D006224:Cricetinae; D003840:Deoxycholic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005998:Glycine / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D007295:Inositol Phosphates / Q000096:biosynthesis; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D018727:Muscarinic Antagonists / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D010766:Phosphorylation; D011869:Radioligand Assay; D051381:Rats; D043587:Receptor, Muscarinic M3; D011976:Receptors, Muscarinic / Q000187:drug effects* / Q000378:metabolism; D013654:Taurine / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology
D001647:Bile Acids and Salts; D018679:Cholinergic Agonists; D007295:Inositol Phosphates; D018727:Muscarinic Antagonists; D043587:Receptor, Muscarinic M3; D011976:Receptors, Muscarinic; D003840:Deoxycholic Acid; D013654:Taurine; D020928:Mitogen-Activated Protein Kinases; D002802:Cholinesterases; D005998:Glycine