title: Dietary and hormonal stimulation of rat exocrine pancreatic function regulates CRHSP-28 phosphorylation in vivo.
abstract: Dietary regulation of digestive enzyme secretion from the pancreas is essential for the breakdown of macronutrients in the gastrointestinal tract. Ca(2+)-responsive heat stable protein (CRHSP)-28 is a regulatory protein that modulates the exocytosis of digestive enzymes from pancreatic acinar cells. In the present study, isoelectric focusing and immunoblotting were used to characterize CRHSP-28 phosphorylation in isolated rat acinar cells and also after hormonal and dietary stimulation of rat pancreas in vivo. CRHSP-28 was highly phosphorylated in isolated acini after stimulation with a physiologic range of concentrations of cholecystokinin-octapeptide (CCK-8). Activation of the high affinity state of the CCK-A receptor with the synthetic peptide JMV-180 confirmed the physiologic relevance of the response. CRHSP-28 phosphorylation was contingent on elevated cellular Ca2+ because it was maximally stimulated by Ca2+ ionophore, but unchanged after protein kinase C, cAMP or cyclic guanosine monophosphate activation. Intravenous infusion of rats with a secretory concentration of the CCK analog, caerulein, stimulated CRHSP-28 phosphorylation by 100% over control (P < 0.01) within 15 min of dosing. Moreover, CRHSP-28 phosphorylation was stimulated by 150% over control (P < 0.05) immediately after consumption of a semipurified AIN-93 diet. These data demonstrate that CRHSP-28 phosphorylation occurs in vivo and can be used as a functional indicator of nutrient-driven acinar cell activation.
authors.affiliation: Department of Nutritional Sciences, University of Wisconsin, Madison, WI 53706, USA.
authors.forename: Kala M
authors.initials: KM
authors.lastname: Kaspar
authors.forename: Diana D H
authors.initials: DD
authors.lastname: Thomas
authors.forename: Ning
authors.initials: N
authors.lastname: Weng
authors.forename: Guy E
authors.initials: GE
authors.lastname: Groblewski
mesh_terms: D000818:Animals; D002118:Calcium / Q000032:analysis / Q000494:pharmacology; D002108:Ceruletide / Q000494:pharmacology; D004032:Diet; D015151:Immunoblotting; D007525:Isoelectric Focusing; D008297:Male; D010179:Pancreas / Q000187:drug effects / Q000502:physiology*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D043886:Receptor, Cholecystokinin A / Q000187:drug effects / Q000502:physiology; D012844:Sincalide / Q000031:analogs & derivatives* / Q000494:pharmacology*
chemical_list: D010750:Phosphoproteins; D043886:Receptor, Cholecystokinin A; C102584:calcium-regulated heat-stable protein 28; C058451:JMV 180; D002108:Ceruletide; D012844:Sincalide; D002118:Calcium