Muscarinic receptors coupled to inositol phospholipid breakdown in human SH-SY5Y neuroblastoma cells: Effect of retinoic acid-induced differentiation.
In human SH-SY5Y neuroblastoma cells, carbachol stimulates inositol phospholipid breakdown with an EC(50) value of 18 ?M. The response is prevented by pirenzepine, with a Hill coefficient of 0.57 and an IC(50) value of 0.15 ?M. A Gpp[NH]p-stimulated [(3)H]phosphatidylinositol-4,5-bisphosphate hydrolysing activity was demonstrated in SH-SY5Y membrane preparations. Treatment of the cells for 3 days with retinoic acid (0.1 and 1 ?M, in 1% ethanol) caused them to differentiate. The ethanol per se increased the incorporation of tritium into the inositol phospholipids following incubation of the cells with [(3)H]myo-inositol. The inositol phospholipid response to carbachol (1000 ?M) was lower following treatment for 3 days with 1 ?M retinoic acid than with 0.1 ?M retinoic acid. The EC(50) values for carbachol, relative rates of stimulation (with respect to that produced by 1000 ?M carbachol) with arecoline, oxotremorine-M and oxotremorine, lack of synergy between carbachol and raised [K(+)] were the same in undifferentiated and retinoic acid-differentiated cells. It is concluded that (a) more than one muscarinic receptor type is coupled to the inositol phospholipid breakdown response in undifferentiated SH-SY5Y cells, and (b) retinoic acid-induced differentiation of the cells does not affect the properties of the muscarinic receptors coupled to the response, although the magnitude of the response appears to be sensitive to the retinoic acid concentration used to induce the cell differentiation.
Fowler
C J
CJ
Department of Geriatric Medicine, Karolinska Institutet, Huddinge Sjukhus, B56, S-141 86 Huddinge, Sweden.
O'Neill
C
C
Almqvist
P
P
Nilsson
S
S
Wiehager
B
B
Winblad
B
B