Norepinephrine-induced calcium mobilization in C6 glioma cells.
Abstract
AIM: 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.
CONCLUSION: 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.
Keywords:
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.
CONCLUSION: 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.