Figure 2

Effects of the GLP-1R inhibitor Exendin (9-39) on the GLP-1-induced enhancement of L-type Ca²⁺currents in isolated canine left ventricular myocytes. A, The time course of the extracellular perfusion of Exendin (9-39, 100 nM) plus GLP-1 (5 nM) is shown. The GLP-1-induced enhancement of Ca²⁺ currents was not blocked by Exendin (9-39), even after washout and reperfusion of these two compounds. The currents were evoked by the depolarizing pulses from a holding potential of -40 mV to 0 mV every 10 s. C, control; E&G, Exendin (9-39) + GLP-1; W, washout. B, Compared to control, the average increase in peak I_Ca was statistically significant in the presence of Exendin (9-39) plus GLP-1 (n = 6, p < 0.05). Panel C shows the time course of I_Ca for control, the extracellular perfusion of 100 nM Exendin (9-39) alone (Exendin (9-39)) and Exendin (9-39) plus 5 nM GLP-1 (GLP-1), and washout (W). The currents were evoked by the pulses depolarizing from holding potential of -40 mV to 0 mV every 10 s. D, The averaged data show that 100 nM Exendin (9-39) applied 5 min ahead of GLP-1 (5 nM) perfusion abolished the GLP-1-induced enhancement of I_Ca (n = 5, p > 0.05).