Regulation of cholecystokinin secretion by peptones and peptidomimetic antibiotics in STC-1 cells.
Peptones are potent stimulants of cholecystokinin (CCK) release in rats, both in vivo and ex vivo in a model of isolated vascularly perfused duodeno-jejunum preparation and in vitro in the intestinal CCK-producing cell line STC-1. The underlying mechanisms were here investigated with this cell line. Protein hydrolysates from various origins (meat, casein, soybean, and ovalbumin; 0.5-1%, wt/vol) dose dependently increased CCK release. Cephalosporin antibiotics, which mimic tripeptides, also stimulated the release of CCK over the concentration range 1-20 mM. The study of concentration dependence of cephalosporin uptake indicated a passive diffusion process at either pH 7.4 or pH 6.0, thus arguing against the involvement of a peptide transporter in CCK secretion. After pertussis toxin treatment (200 ng/ml; 5 h), the peptone- and cephalexin-induced CCK secretion was significantly reduced, suggesting the involvement of pertussis toxin-sensitive heterotrimeric G protein(s) in the secretory activity of STC-1 cells. Consistent with this was the identification by Western blot of G(i2)alpha, G(i3)alpha, and G(o)alpha immunoreactivities in STC-1 cell extracts. Additionally, peptones and cephalexin increased the cellular content in inositol phosphates, whereas a mild increase in cAMP content was restricted to peptone-treated cells. Protein kinase A or C inhibition did not modify peptone- or antibiotic drug-evoked CCK release. The extracellular Ca2+ chelator EGTA (500 microM) and the intracellular Ca2+ chelator BAPTA-AM [1,2-bis-(O-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl) ester; 20 microM] abolished the peptone- and antibiotic drug-induced CCK release. Nifedipine and verapamil (10 microM) reduced by about 50% the CCK secretion evoked by these two secretagogues. In conclusion, peptones and some cephalosporins are potent stimulants of CCK release in the STC-1 cell line. The cellular mechanisms involve pertussis toxin-sensitive G protein(s) and are dependent on Ca2+ availability. We suggest that the STC-1 cell line is a useful model to study the molecular basis of peptone-induced CCK secretion.
Némoz-Gaillard
E
E
INSERM U-45, Hôpital E. Herriot, Lyon, France.
Bernard
C
C
Abello
J
J
Cordier-Bussat
M
M
Chayvialle
J A
JA
Cuber
J C
JC
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002506:Cephalexin / Q000494:pharmacology; D002511:Cephalosporins / Q000494:pharmacology*; D002766:Cholecystokinin / Q000378:metabolism*; D000242:Cyclic AMP / Q000096:biosynthesis; D019204:GTP-Binding Proteins / Q000502:physiology; D007422:Intestines / Q000187:drug effects*; D051379:Mice; D010461:Peptones / Q000494:pharmacology*; D037342:Pertussis Toxin; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D002511:Cephalosporins; D010461:Peptones; D010566:Virulence Factors, Bordetella; D002766:Cholecystokinin; D000242:Cyclic AMP; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D002506:Cephalexin; D002118:Calcium