Figure 6

Measurements of Ca²⁺ mobilization from intracellular stores and Ca²⁺ influx over the plasma membrane. (A) Effects of 0.2 mmol/L CCh on changes in [Ca²⁺]_i in islets from GK rats treated with ARA290 compared with placebo treatment. Bars above the traces indicate the duration of stimulation. The values 0 CaCl₂ and 2.56 CaCl₂ indicate 0 mmol/L and 2.56 mmol/L CaCl₂ respectively. The concentration of CCh is 0.2 mmol/L. Phase I shows changes in [Ca²⁺]_i in response to CCh in the absence of extracellular Ca²⁺. Phase II shows effects of adding 2.56 mmol/L CaCl₂ in the perifusion chamber on changes in [Ca²⁺]_i, indicating Ca²⁺ influx over the plasma membrane. Phase III shows changes in [Ca²⁺]_i in response to CCh in the presence of extracellular Ca²⁺. The displayed traces are representatives of 13 traces from the placebo-treated rats (n = 4) and 19 traces from ARA290-treated rats (n = 4). (B) Phase I: Average Δ peak [Ca²⁺]_i values, that is, fura-2 ratio, in islets stimulated with CCh in the Ca²⁺ free buffer; Phase II: Average basal Ca²⁺ influx over the plasma membrane; Phase III: Average Δ peak fura-2 ratio in islets stimulated with CCh in the presence of extracellular Ca²⁺. Data are shown as means ± SEM. P values between the two groups (PBS placebo, black bars, versus ARA290, red bars) are shown. *P < 0.05, **P < 0.01, N.S. indicates no statistical significance.