Fig. 5.

Effect of GLP-1 on Ca²⁺ oscillations in control and βTpcn2 KO islets. (A, B) Example traces of control islets (blue) and β-cell-specific Tpcn2 KO islets (black), showing Ca²⁺ responses to 8 mM glucose with the addition of GLP-1. Boxes in (B) indicate regions shown in (C). (C) Example Ca²⁺ oscillations before and after the addition of GLP-1 after the 8 mM glucose response in a KO islet. The Ca²⁺ signal, as observed during a single oscillation (image capture at 2 s intervals) is apparent across the whole islet. The increase in oscillation frequency is apparent between the upper (−GLP-1) and lower (+GLP-1) traces. Scale bar = 20 μm. (D, E) Change in oscillation frequency upon GLP-1 stimulation normalised to the rate induced by 8 mM glucose. Oscillations were counted in a 5 min window before and after GLP-1 addition and the red dotted line indicated the average increase. p < 0.05 for the effects of GLP-1 in each case. (F) Quantification of the increase in oscillation frequency, showing no significant difference between control and βTpcn2 KO islets (mean ± SEM). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)