Exendin-4 increases [Ca²⁺]_i and cAMP content in mouse β-cells.

<p>A, A single fura-2 loaded and Ad-MtLuc-RFP-infected mouse β-cell was imaged to determine the [Ca²⁺]_I, at 5.6 mM glucose in KRBH. After establishment of a stable baseline [Ca²⁺]_i, 10 nM Ex-4 was applied for 25 sec (indicated by horizontal bars). Note that a repeatable increase of [Ca²⁺]_i was measured. B, Population study conducted at the single cell level in which the action of Ex-4 to increase [Ca²⁺]_i was evaluated in β-cells not infected (open bars) or infected with Ad-MtLuc-RFP (filled bars). For these experiments, the KRB contained 5.6 or 7.5 mM glucose, as indicated. A response to Ex-4 was defined as a >100 nM increase of [Ca²⁺]_i occurring in a single β-cell. C, Ex-4 caused a dose-dependent increase in cAMP content in mouse islet cells in KRB containing 7.5 mM glucose without or with Ad-MtLuc-RFP infection.