Creatine phosphate as energy source in the cerulein-stimulated rat pancreas study by31P nuclear magnetic resonance

Abstract

Stimulation of the rat exocrine pancreas by cerulein induces a variety of cellular processes, some of which require the expenditure of energy. In this study, changes in the amounts of various energy metabolites, including creatine phosphate (PCr), ATP, and ADP were determined by high-resolution 31P NMR spectroscopy. The spectrum of a perchloric acid extract of pancreas from the 48 h fasted rat was taken as a reference for comparison of 31P NMR spectra recorded after stimulation by cerulein. The NMR results obtained from rat pancreas stimulated in vivo by cerulein (3, 5, 10, 20, 40 min) were compared to those determined by HPLC. We show that during hormonal stimulation, the relative concentrations of PCr in the pancreas of the fasted rat rise significantly (p less than 0.02), reach a maximum at 10 min, fall between the 10th and 20th min, and then return to the relatively low levels observed in controls. On the other hand, the relative concentrations of ATP fall during the first 10 min after stimulation by cerulein, then rise significantly between the 10th and 20th min, whereas the levels of ADP rise during the first 10 min and fall between the 10th and 20th min. The energy required for exocytosis was assumed to be supplied by ATP synthesized in acinar cells. The 31P NMR results indicated that this ATP was derived from phosphorylation of ADP by PCr, and that large amounts of PCr are synthesized during the first minutes after cerulein stimulation. In addition, a significant rise in glycerophosphocholine was observed after cerulein stimulation, which was attributed to an enhanced catabolism of membranes and an increase in phospholipid turnover. Injection of cerulein antagonists, such as asperlicin or lorglumide, inhibited the effects of cerulein stimulation on energy metabolites. Furthermore, no changes were observed after injection of secretin, a hormone that stimulates secretion of bicarbonate. However, the analog of cerulein, pentagastrin, produced the same effects as cerulein, although to a lesser extent.