Fig. 6.
Phenylalanine increases intracellular Ca2+ ([Ca2+]i) in intestinal CCK-GFP cells. Isolated CCK-expressing GFP cells were prepared from CCK-GFP transgenic mice and identified by endogenous GFP fluorescence (left, GFP). All cells were loaded with 2.5 μM X-Rhod-1 (X-Rhod-1) and identified by fluorescence using an RFP filter. Overlays of GFP and X-Rhod-1 images are shown (overlay). The same GFP-positive cells were imaged following addition of 30 mM l-alanine (row on top) or 10 mM l-phenylalanine (row on bottom). Increases in Ca2+ fluorescence were indicated by increased brightness (greater red intensity). As shown in the bottom right, an elevation in [Ca2+]i was seen within 1.4 min and lasted for >3.6 min following phenylalanine administration. In contrast, alanine did not produce an elevation in [Ca2+]i. Results are representative of >20 cells studied.