title: The human astrocytoma cell line 1321 N1 contains M2-glandular type muscarinic receptors linked to phosphoinositide turnover.
abstract: 1. Muscarinic receptors present in the human astrocytoma cell line 1321 N1 were characterized in radioligand binding studies and in functional studies of carbachol-stimulated phosphatidylinositol (PI) turnover. 2. In radioligand binding studies the muscarinic receptor in intact cells could be labelled using [3H]-N-methylscopolamine ([3H]-NMS) but not by [3H]-pirenzepine. In the intact cells these receptors displayed low pirenzepine affinity (pKi = 6.83) indicating that they were not of the M1 subtype. Furthermore, the 1321 N1 muscarinic receptors displayed low affinity for the two M2-cardiac selective ligands methoctramine (pKi = 5.82) and AF-DX 116 (pKi = 6.29). This pharmacology was consistent with the 1321 N1 cells containing a single population of muscarinic receptors that displayed a similar pharmacology to the M2-receptor present in exocrine gland tissue. 3. The M2-gland nature of the receptors was further indicated in the functional studies where antagonist affinities were determined from their ability to antagonize carbachol-stimulated PI turnover in 1321 N1 cells. pA2 values for pirenzepine (7.31), methoctramine (6.10) and AF-DX 116 (6.52) were similar to those determined in the binding studies. 4. From these studies we conclude that 1321 N1 astrocytoma cells contain an M2-gland muscarinic receptor which mediates muscarinic receptor-mediated stimulation of PI turnover in these cells.
authors.affiliation: Department of Pharmacology, Syntex Research Centre, Palo Alto, CA 94304.
authors.forename: E A
authors.initials: EA
authors.lastname: Kunysz
authors.forename: A D
authors.initials: AD
authors.lastname: Michel
authors.forename: R L
authors.initials: RL
authors.lastname: Whiting
authors.forename: K
authors.initials: K
authors.lastname: Woods
mesh_terms: D000818:Animals; D001254:Astrocytoma / Q000032:analysis; D001667:Binding, Competitive; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism*; D008297:Male; D019832:N-Methylscopolamine; D010890:Pirenzepine / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D011976:Receptors, Muscarinic / Q000032:analysis*; D012602:Scopolamine Derivatives / Q000378:metabolism; D013403:Sugar Phosphates / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D007295:Inositol Phosphates; D011976:Receptors, Muscarinic; D012602:Scopolamine Derivatives; D013403:Sugar Phosphates; D010890:Pirenzepine; D019832:N-Methylscopolamine