Pertussis toxin effect on carbachol-elicited stimulation of phosphoinositide hydrolysis in human neuroblastoma [SK-N-BE(2)]

Charbachol (Cch) dose-dependently elicited accumulation of [3H]inositol phosphates (IPs) in human neuroblastoma cells SK-N-BE(2) prelabelled with [3H]myo-inositol and stimulated in the presence of 10 mM Li+. Cell response was observed at agonist concentrations higher than 10-6 M and was nearly maximal at 10-3 M; Cch concentration eliciting half- maximal stimulation of [3H]IPs production was about 3.3 x 10-5 M. Pirenzepine (PZ) inhibited [3H]IPs production, as elicited by 1 mM CCh in the presence of 10 mM Li+, in the concentration range 10-8 -10-4 M, with half maximal effect at 2.5 x 10-7 M. Cell treatment with pertussis toxin (PTX) (100 ng/ml for 6 h) resulted in a 20% reduction of total [3H]IPs accumulation elicited by cell stimulation with 1 mM Cch. Results indicate that the human neuroblastoma cell line SK-N-BE(2) possesses a population of muscarinic receptors, highly sensitive to PZ and coupled to stimulation of phosphoinositide hydrolysis through a mechanism which is only partially sensitive to PTX