PubMed · 4610299
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W A Olsen. 1974. Carbohydrate absorption.. https://doi.org/10.1016/s0025-7125(16)32079-x
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To investigate the role of phospholipids in exocytotic secretory events, we utilized rat pancreatic acinar AR42J cells that secreted amylase in response to cholecystokinin octapeptide (CCK-8). Wortmannin, an inhibitor of phosphoinositide 3-kinase (PI3K), was found to inhibit the secretion in a dose-dependent manner. When changes in cell membrane phospholipids were investigated before and after CCK-8 stimulation using [32P]orthophosphoric acid-labeled AR42J cells, we observed a rapid increase in phosphatidic acid (PtdOH) levels right after stimulation, which was not observed in non-stimulated cells. The increase, however, was suppressed by wortmannin pre-treatment, which also inhibited amylase secretion. Changes in other major phospholipids were not significant. These results indicate that CCK-8 induces amylase secretion through PI3K-regulated production of PtdOH in cell membranes.
Leptin originally described as product of the ob gene has been shown to be expressed in various tissues including the gastrointestinal tract. In this study, we investigated the influence of leptin on the secretion of pancreatic juice in biliary-pancreatic duct cannulated anaesthetised rats and in dispersed rat pancreatic acini in vitro. Exogenous leptin was given in boluses intravenously with or without CCK-8 (12 pmol kg(-1) body weight) in the presence or absence pharmacological CCK(1) receptor blockade, cervical vagotomy, and capsaicin pre-treatment. Administration of leptin (0.1, 1 and 10 microg kg(-1) body weight) did not affect the volume of bile and pancreatic juice while the protein and trypsin outputs were reduced in a dose-dependent manner. In the rats, leptin inhibited CCK-8 stimulated protein and trypsin outputs stronger than the basal pancreatic secretion. The inhibition by leptin was abolished by the pharmacological CCK(1) receptor blockade, cervical vagotomy, and capsaicin pre-treatment. In contrast, leptin did not affect basal and CCK-8-stimulated amylase release from the dispersed rat pancreatic acini in vitro. In conclusion, the results of the present study suggest that leptin does not act directly on the rat pancreatic acinar cells but inhibits the secretion of pancreatic enzymes acting indirectly via a neurohormonal CCK-vagal-dependent mechanism.
The present study was undertaken to examine the factors that regulate rat serum (RS)- and nerve growth factor (NGF)-induced differentiation in a rat parotid acinar cell line. RS elicited extracellular signal-regulated kinase (ERK1/ERK2) activation within 5min, while cyclic AMP (cAMP) levels transiently rose after 6hr. RS also elicited a rise in amylase mRNA levels within 30min, which preceded the rise in amylase protein levels. A possible role for NGF was suggested by the findings that parotid cells express both TrkA and p75 receptors. The immunoreactivity of these NGF receptors was reduced during exposure to RS. Following prolonged incubation in RS when ERK activity subsided to near basal levels, NGF restored ERK1/ERK2 activity to the elevated level initially observed in RS. NGF was ineffective when cells were incubated in fetal bovine serum. NGF, when incubated in combination with the cAMP-generating neuropeptides, calcitonin gene-related peptide and vasoactive intestinal peptide, markedly enhanced the cellular amylase content produced by RS. We conclude that parotid cell differentiation arises from an activation of cell surface receptors by humoral factors in combination with NGF and cAMP-generating neuropeptides.