Phenylalanine-stimulated secretion of cholecystokinin is calcium dependent.
The secretion of cholecystokinin was examined in STC-1 cells, an intestinal cholecystokinin (CCK)-secreting cell line. Exposure to the amino acid L-phenylalanine increased release of CCK by 135%, 180%, and 251% of control levels after 15-min treatments with 5, 20, and 50 mM phenylalanine, respectively. L-Phenylalanine-induced secretion of CCK was inhibited by the calcium channel blocker diltiazem (10 microM). L-Phenylalanine (20 mM) also significantly increased cytosolic calcium levels in fura 2-acetoxymethyl ester (fura 2-AM)-loaded cells, and this increase was diltiazem sensitive. D-Phenylalanine, over the dose range of 5-50 mM, produced nonsignificant increases in CCK release. Treatment of STC-1 cells with 300 ng/ml of pertussis toxin for either 4 or 24 h did not significantly affect either basal release of CCK or L-phenylalanine-stimulated secretion. Patch-clamp recordings from cell-attached membrane patches showed a stimulation in calcium channel activity after L-phenylalanine. These results indicate that, in STC-1 cells, L-phenylalanine stimulates release of cholecystokinin via a calcium-dependent process.
Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710.
A W
AW
Mangel
V
V
Prpic
H
H
Wong
S
S
Basavappa
L J
LJ
Hurst
L
L
Scott
R L
RL
Garman
J S
JS
Hayes
A I
AI
Sharara
N D
ND
Snow
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D002766:Cholecystokinin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004110:Diltiazem / Q000494:pharmacology; D004594:Electrophysiology; D005453:Fluorescence; D019204:GTP-Binding Proteins / Q000378:metabolism; D051379:Mice; D010649:Phenylalanine / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D015220:Calcium Channels; D010649:Phenylalanine; D002766:Cholecystokinin; D019204:GTP-Binding Proteins; D004110:Diltiazem; D002118:Calcium