Figure 6. Intracellular Ca²⁺ concentration, [Ca²⁺]_i changes associated with glucose stimulation in different fluorescent cells.

(a) Glucose responsiveness of GFP⁺ stable HIT-T15 cells. The green line represents a GFP⁺ cell in basal (3 mM, left panel) and stimulatory (14 mM, right panel) levels of glucose. The other lines (red, blue, and orange) represent non-fluorescent cells. (b) No glucose responsiveness of mCherry⁺ stable HIT-T15 cells was observed. (c) Fluorescence traces from INS-1 cells. Each color represents a different cell, indicating spontaneous Ca²⁺ oscillations arising from action potentials.