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We determined whether La3+ enter human peripheral blood lymphocytes via Na+/Ca2+ exchanger (measured with fura-2). We first compared the sensitivity of fura-2 with La3+ and Ca2+, the result indicates that the sensitivity of fura-2 for La3+ is much greater than for Ca2+. La3+ forms a 1:1 La3+-fura-2 complex (apparent dissociation constant =1.7(10-12mol/L, pH 7.05). Ouabain-pretreated cells, suspended in Na+-free medium, showed that La3+ can enter human lymphocytes via the Na+i/Ca2+ (La3+)o exchanger and is found to be about 10-12 mol/L in cells exposed to 0.4 mmol/L La3+. Otherwise, the higher concentration (0.1 mmol/L) blocks the Na+i/Ca2+(La3+)o exchange-mediated influx of Ca2+, but the lower concentration (0.01 mmol/L) appears to increase Ca2+ entry.
We first compared the sensitivity of fura-2 with La3 + and Ca2 +, the results indicates that the sensitivity of fura-2 for La3 + is much greater than for Ca2 +. La3 + forms a 1: 1 La3 + -fura-2 complex (apparent dissociation constant = 1.7 (10-12 mol / L, pH 7.05). Ouabain-pretreated cells, suspended in Na + -free medium, showed that La3 + can enter human lymphocytes via the Na + i / Ca2 + (La3 +) o exchanger and is found to be about 10-12 mol / L in cells exposed to 0.4 mmol / L La3 +. Otherwise, the higher concentration (0.1 mmol / L) blocks the Na + i / Ca2 + (La3 +) o exchange-mediated influx of Ca2 +, but the lower concentration (0.01 mmol / L) appears to increase Ca2 + entry.