FIGURE 6.

Interplay of different types of extracellular autocrine signaling factors regulates the activity of MIN6 cells (ai) [Ca²⁺]_i oscillations in glucose‐stimulated MIN6 cells stopped in the presence of recombinant apyrase (10 U), to recover upon addition of oleic acid (100 µM). (aii) As a control, pre‐washed MIN6 cells were treated with oleic acid (100 µM), which evoked even stronger responses in [Ca²⁺]_i oscillations. (b) Addition of ATP or ATPγS (50 µM) to FAF‐BSA‐ treated MIN6 cells yielded a single high‐intensity [Ca²⁺]_i transient but did not evoke spontaneously occurring continuous [Ca²⁺]_i oscillations. (c) Addition of recombinant apyrase (10 U) reduced and stopped [Ca²⁺]_i oscillations in MIN6 cells. Subsequent application of oleic acid (100 µM) partly resumed [Ca²⁺]_i oscillations which was finally stopped by the addition of the GPR40 antagonist GW1100 (25 µM), pointing to an interplay of various autocrine extracellular signaling factors that regulate cell activity. Imaging was performed in the presence of 11 mM glucose. Washes are indicated by ▼