APStracts 2:0173G, 1995.

B-adrenergic regulation of cholecystokinin secretion in stc-1 cells. Scott, Leann, Veronica Prpic, Wm. Darrell Capel, Srisaila Basavappa, Allen W. Mangel, Thomas W. Gettys, and Rodger A. Liddle. Departments of Medicine and Cell Biology, Duke University Medical Center, Durham, NC 27710, Department of Physiology, University of Oxford, Oxford OX1 3PT, UK, Department of Medicine, Medical University of South Carolina, Charleston, SC 29425

APStracts 2:0173G, 1995.

Previously, it has been shown that an increase in cAMP levels stimulates intestinal secretion of CCK; however, the mechanisms for increasing intracellular cAMP levels are not known. Using the CCK -secreting intestinal cell line, STC-1, we evaluated whether [beta] -ARs might be present on STC-1 cells and whether they stimulated CCK release through increases in cAMP. Photoaffinity labeling of [beta] -ARs from solubilized STC-1 cell membranes revealed photoincorporation of the agonist [125I]-iodocyanopindolol into an approximate 75 kDa band. Addition of the [beta]-AR agonist, isoproterenol, in the presence of IBMX, produced a concentration-dependent increase in both cAMP levels and CCK release. Blockade of [beta]1- and/or [beta]2-ARs significantly inhibited isoproterenol-stimulated increases in cAMP production and CCK release. Using fura-2 loaded cells to measure changes in intracellular calcium ([Ca2+]i), isoproterenol stimulation was found to increase cytosolic calcium levels. To evaluate whether this increase in [Ca2+]i was due to release of Ca2+ or influx of Ca2+, cells were treated with the L-type calcium channel blocker, diltiazem, which inhibited isoproterenol-stimulated CCK secretion. Furthermore, in patch-clamp studies with inside-out membrane patches, addition of the catalytic subunit of protein kinase A activated diltiazem-sensitive calcium channels. It is concluded that [beta]-ARs are present on STC-1 cells and are coupled to the production of cAMP, which may increase CCK release through a calcium-dependent process.

Received 6 February 1995; accepted in final form 3 August 1995.
APS Manuscript Number G49-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 August 1995.