Aim: To observe the effects of methylflavonolamine (MFA) on free intracellular calcium concentration ([Ca2+]i) of isolated embryonic rat brain cells in presence and absence of high extracellular potassium and L-glutamate.
Methods: [Ca2+]i was measured in a spectrofluorophotometer by preloading the cells with calcium sensitive fluorescent indicator Fura 2-AM.
Results: Resting [Ca2+]i was 197 +/- 20 nmol.L-1 (n = 44) in the presence of Ca2+ 1.3 mmol.L-1 in Hanks' solution. MFA 0.15 mmol.L-1 had no effect on the resting [Ca2+]i. When extracellular Ca2+ was 1.3 mmol.L-1, MFA (0.03-0.3 mmol.L-1) concentration-dependently inhibited the [Ca2+]i elevation induced by high extracellular potassium, with an IC50 value of 0.14 (95% confidence limits: 0.05-0.42) mmol.L-1. At higher concentration (0.15-0.30 mmol.L-1), MFA decreased L-glutamate-induced [Ca2+]i elevation, with an IC50 of 0.20 (95% confidence limits: 0.01-3.40) mmol.L-1.
Conclusion: MFA inhibited Ca2+ influx through voltage-dependent calcium channel and, at higher concentration, through receptor-operated calcium channel in the embryonic rat brain cells.