Increase in pancreatic amylase mediated by glucocorticoid

The role of endogenous glucocorticoids in rat experimental models of acute pancreatitis

BACKGROUND & AIMS

Cytokines activate the hypothalamic-pituitary-adrenal axis and suppress inflammation by stimulating glucocorticoid secretion. The state of adrenocortical function during acute pancreatitis and its role in this disease were determined.

METHODS

Cerulein-induced pancreatitis or closed duodenal loop pancreatitis was produced in rats that had undergone adrenalectomy or sham adrenalectomy, and the serum corticosterone and interleukin 8 levels and the intensity of the pancreatitis were examined.

RESULTS

Serum corticosterone levels were significantly higher than basal levels in both models of experimental pancreatitis. In both models, adrenalectomy increased serum amylase and pancreatic edema and produced more severe inflammation. Adrenalectomy significantly increased mortality in animals with closed duodenal loop pancreatitis. Exogenous hydrocortisone administered to adrenalectomized animals suppressed the elevation of serum interleukin 8 levels and decreased both the severity of pancreatitis and mortality.

CONCLUSIONS

These results suggest that the adrenocortical function is stimulated during acute pancreatitis and that the secretion of endogenous glucocorticoids may play an important role in mitigating the progress of this disease, probably by inhibiting cytokine production.

Glucocorticoids increase amylase mRNA levels, secretory organelles, and secretion in pancreatic acinar AR42J cells

Previous studies have suggested a role for glucocorticoids in the differentiation of the acinar pancreas. We have now used the rat tumor cell line AR42J, derived from the acinar pancreas, to directly study this effect of glucocorticoids in vitro. The steroid hormones dexamethasone, corticosterone, aldosterone, and progesterone, but not estrogen, increased both the amylase content and the number of secretory granules of these cells. The potencies of the steroids were directly related to their effectiveness as glucocorticoids; dexamethasone was the most potent hormone and gave maximal effects at 100 nM. Morphometric analyses revealed that dexamethasone increased the volume density of granules 5.5-fold from 0.20 +/- 0.08 to 1.10 +/- 0.20% (n = 4) of the cytoplasmic volume. Dexamethasone treatment also increased the volume density of rough endoplasmic reticulum 2.4-fold from 1.20 +/- 0.09 to 2.86 +/- 0.30% (n = 5) of the cytoplasmic volume. After 48 h of dexamethasone treatment the cellular content of amylase increase eightfold from 2.8 +/- 0.4 to 22.6 +/- 3.8 U/mg protein (n = 6). This effect of dexamethasone was discernible after 12 h of incubation and approached maximal stimulation after 72 h of incubation. The increases in cellular amylase content were due to increased amylase synthesis as shown by specific immunoprecipitation of [35S]methionine-labeled proteins. Moreover, in vitro translation of cellular mRNA indicated that dexamethasone treatment increased amylase mRNA. Dexamethasone treatment also led to increased secretion of amylase in response to the secretagogue cholecystokinin. These data indicate, therefore, that glucocorticoids induce a more highly differentiated phenotype in AR42J pancreatic cells, and they suggest that glucocorticoids act via the enhanced transcription of specific mRNAs for acinar cell proteins.

Fetal and neonatal rat pancreas in organ culture: age-related effects of corticosterone on the development of the islet cells

Fetal (18 days postcoitum) and neonatal (3-day) pancreatic explants were grown in organ culture with or without supplementation with corticosterone (0.1 micrograms/ml). After 0, 4, and 8 days of culture, the specific hormone-positive, islet cell volumes were determined by the use of immunocytochemical and morphometric methods. The insulin, glucagon, and somatostatin contents of the explants were estimated by radioimmunoassays. In the fetal explants, all of the islet cell populations increased in volume and the content of each of the hormones increased over an 8-day period of culture. Supplementation with corticosterone resulted in a restriction of the increases of the alpha and delta cell volumes and in the somatostatin content of the explants. In the neonatal explants, the volumes of the alpha and delta cells and the glucagon and somatostatin contents decreased over a 4-day culture period. The presence of corticosterone in the culture medium preserved these cells and their hormone content. Co-culture of 18-day fetal and 3-day neonatal pancreata in control medium for 8 days resulted in a significant decrease in the content of all three of the islet hormones in the fetal explants. These results suggest that a substance harmful to the islet cells is released from the degenerating acinar cells. Thus, the effects of the steroid on the islets may be mediated through its effects on the acinar tissue.