Fig. 7.

A: transfection of STC-1 cells with siRNA targeting SNAT2 for either 72 h (left) or 96 h (right) significantly reduced Ca²⁺ signaling in response to 1 mM l-proline, compared with cells transfected with NT siRNA. B: responses of STC-1 cells to different amino acids (added at the times marked by the downward arrows) or MeAIB are blocked by the L-type voltage-sensitive Ca²⁺ channel blockers, either nifedipine or nitrendipine. Traces show responses in STC-1 cells incubated in the absence or in the presence of nifedipine at 1 μM. Nifedipine or nitrendipine was added to the cells 2–5 min before the addition of amino acids at 5 mM, or MeAIB at 10 mM. Two separate experiments are superimposed in each panel. For clarity, starting [Ca²⁺]_i were translated to align. Insets show percent inhibition of the responses to nifedipine at 1 μM (solid bars), nifedipine at 10 μM (shaded bars), and nitrendipine at 1 μM (open bars).