Norepinephrine-induced calcium mobilization in C6 glioma cells.
OBJECTIVE
To investigate the mechanism underlying the norepinephrine-induced elevation in intracellular calcium concentration ([Ca2+]i) in C6 glioma cells.


METHODS
Measurement of [Ca2+]i was carried out using the dual-wavelength fluorescence method with fura-2 as the indicator.


RESULTS
Norepinephrine was found to induce concentration-dependent increases in [Ca2+ ]i through alpha1-adrenoreceptors. The [Ca2+]i elevations were extracellular-calcium independent and not influenced by the treatment of pertussis toxin. Pretreatments with either U73122 or thapsigargin abolished the subsequent cellular calcium responses to norepinephrine. Preincubation with phorbol 12-myristate 13-acetate (PMA) significantly reduce d the [Ca2+]i elevations, while protein kinase C inhibitors Ro31-8220 or GF-109203X completely blocked the inhibitory action of PMA. However, drugs either activating or inhibiting the function of protein kinase A had no effect on the [Ca2+]i elevations.


CONCLUSIONS
Norepinephrine induces calcium mobilization from internal stores by activation of phospholipase C in C6 cells. The [Ca2+]i elevation is negatively regulated by the activation of protein kinase C.
Han
Jian-Zhong
JZ
Neuroscience Research Institute and Department of Neurobiology, College of Pharmacy, Second Military Medical University, Shanghai 200433, China.
Lin
Wen
W
Lou
Shu-Jie
SJ
Chen
Yi-Zhang
YZ
D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D016257:Fura-2; D005910:Glioma / Q000378:metabolism* / Q000473:pathology; D009638:Norepinephrine / Q000494:pharmacology*; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism; D014407:Tumor Cells, Cultured
D011942:Receptors, Adrenergic, alpha; D011493:Protein Kinase C; D002118:Calcium; D016257:Fura-2; D009638:Norepinephrine