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 usingIn the intact cells these receptors displayed low pirenzepine affinity (pKi = 6.83) indicating that they were not of the M1 subtype. Furthermore, the 1321 Ni 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 NI 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 Ni 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.

mRNA coding for neurotransmitter receptors in a human astrocytoma.

“…Similarly, the presence of glutamate receptor mRNAs in the human astrocytoma R-111 is in line with numerous reports that rat astrocytes possess glutamate receptors (4)(5)(6)(7)(8)(9)(10). Furthermore, the presence of an astrocytoma R-111 mRNA encoding muscarinic AcCho receptors, which couple to the inositol phosphate system in the oocytes, also agrees with the finding of similar receptors in the human astrocytoma cell line 1321 N1 (39)(40)(41). In spite of these important similarities some differences exist between our results and previous works.…”

The interaction of parafluorohexahydrosiladiphenidol at muscarinic receptors in vitro

“…The pA2 values for pirenzepine, AF-DX 116, 4-DAMP and methoctramine in the rat aorta (Choo et al, 1986;, rabbit ear artery (Hynes et al, 1986) and bovine coronary artery (Duckles, 1988) were similar to those observed in ileal smooth muscle (Kunysz et al, 1989). However, anomalous pA2 values for pFHHSiD were found in some isolated tissues.…”

“…Human astrocytoma cells (1321 Ni) were cultured and phosphatidylinositol hydrolysis studies were conducted as described previously (Kunysz et al, 1989). Human SH-SYSY cells were cultured at 370C in a humidified atmosphere as a monolayer culture in a medium consisting of 45% Hams F12, 45% Dulbecco's modified Eagle's medium (DMEM) and 10% foetal calf serum.…”

“…Phosphatidylinositol hydrolysis was studied in the SH-SY5Y cell line after the method of Kunysz et al (1989) as follows: the cells were harvested as described above and incubated for 12 h, at a density of 5 x 106 cells ml-1, in a medium consisting of Hams FO0 and 0.1% BSA and 1 yCimlP1 [3H]-myo-inositol. After washing the cells twice with buffer to remove excess [3H]-myo-inositol, the cells were resuspended in 0.75ml of oxygenated modified Krebs-Bicarbonate buffer (see below for composition).…”

Calcium‐dependence of histamine‐ and carbachol‐induced inositol phosphate formation in human U373 MG astrocytoma cells: comparison with HeLa cells and brain slices

“…The dependence of phosphoinositidase ' (PIC) on low levels of intracellular Ca24 has also been demonstrated in these cells (Tilly et al, 1990a). However, it has been suggested that in non-excitable cells, such as epithelia, Ca2+ entry mechanisms may be confined to that associated with the refilling of 1,4,5-IP3-sensitive intracellular stores (Putney, 1990 (Kunysz et al, 1989). In rat cerebral cortex the response to muscarinic agonists appears to be mediated predominantly by MI-receptors (Forray & El-Fakahany, 1990 there is also a clear species difference between rat and guineapig cerebral cortex, which is also evident in the data of Alexander et al (1990b) over a more limited range of Ca2" concentrations.…”