No abstract

We used a monoclonal antibody against an epitope located in the N-terminal moiety of the rat glucocorticoid receptor to identify the glucocorticoid receptor-containing cells in the rat pancreas. Monospecific polyclonal antisera against insulin, glucagon, somatostatin, and amylase were applied to serial sections in colocalization studies to identify the respective endocrine and exocrine cells. Glucocorticoid receptor immunoreactivity was exclusively present in nuclei and cytoplasm of the beta-cells of pancreatic islets. Western blots using the glucocorticoid receptor antibody resulted in identical 94K immunoreactive proteins in both liver and pancreas. After adrenalectomy, the glucocorticoid receptor immunoreactivity of beta-cells decreased significantly. A computer-assisted method of semiquantitative evaluation of the glucocorticoid receptor immunoreactivity demonstrated a significant decrease in the staining intensity of the beta-cells by 23.5% and in that of insulin antibodies by 10.4%, while amylase immunoreactivity was only slightly decreased. Serum levels of corticosterone determined by RIA decreased from 225 micrograms/ml in sham-operated animals to 55 micrograms/ml in animals 14 days after adrenalectomy, while the tissue content of amylase decreased by 45%. The immunohistochemical findings give circumstantial evidence of the presence of glucocorticoid receptor in beta-cells. We interpret our data as indicating an indirect effect of glucocorticoids on amylase synthesis via a glucocorticoid-insulin-exocrine cell pathway.

No abstract

Glycollate oxidase (glycollate: oxygen oxidoreductase, EC 1.1.3.1) was purified to apparent homogeneity from crude extracts of greening cucumber cotyledons (Cucumis sat vus). Molecular sieving and chromatofocusing resulted in 700-fold purification and specific activity of 1 μkat mg(-1) protein. The enzyme exhibited a Mr of 180,000, or 700,000, respectively, and is a tetramer or 16-mer made of identical subunits of Mr 43,000. Monospecific antibodies were raised against the homogeneous protein.

Continuous intravenous infusion of caerulein (0.25 pg . kg-' . h -l ) has recently been reported [Schick, J., Kern, H. & Scheele, G. (1984) J. Cell Bid. 99, 1569 to enhance significantly the synthesis of both trypsinogen and chymotrypsinogen and to decrease that of amylase in the rat pancreas. With a view to achieving a better understanding of the mechanisms underlying caerulein modulation of pancreatic gene expression, the relative levels of active mRNA corresponding to these proteins were determined in caerulein-stimulated animals and compared to those ofcontrols infused with a 0.9% NaCl solution. For this purpose, the translation products synthesized in vitro in a rabbit reticulocyte lysatc translation system were measured. Prolonged caerulein infusion had less pronounced effects on mRNA levels as determined by the relative synthesis of translation products than on individual secretory proteins. No changes in mRNA levels were observed during 6 h of hormonal stimulation, whereas a 7-fold increase in the ratio of trypsinogen to amylase synthesis was obtained previously. After 24 h of caerulein infusion, only a slight change in active mRNA coding for amylase (1.7-fold) and serine protease zymogens (1.4-fold) occurred as compared to 14-fold and 2-fold variations in the synthesis rates of the corresponding proteins. These findings indicate that caerulein exerts a predominantly translational control on thc biosynthesis of pancreatic amylase, trypsinogen and chymotrypsinogen even after 24 h of hormonal stimulation.However, additional control at a transcriptional or post-transcriptional level (i.e. via messenger RNA stability) may well take place.Caerulein, a peptide which was originally isolated from the skin of the frog Hylea cclerulea, has been characterized as a secretagogue which acts on pancreatic cells by increasing the output of amylase [l]. This action on pancreatic enzyme secretion results fLDm the ability of caerulein to cause both a movement of celluiar calcium [l] and an increase in cellular cyclic G M P [2, 31. Besides its ability to enhance protein secretion, caerulein is known to induce depolarization of pancreatic acinar cells [4] as well as to have various other effects [5 -71. The striking stimulatory action of caerulein on pancreatic secretion is not surprising, since this decapeptide hormone shares with porcine cholecystokinin [8] the same C-terminal pentapeptide sequence which is known to be responsible for biological activity. A number of other caerulein-related peptides (cholecystokinin-like hormones) have also been identified in amphibians and, interestingly, have been found to have their counterparts in the mammalian gut [9].Secretion of pancreatic enzymes under cholecystokininrelated peptide stimulation has been well documented in a variety of mammalian species [lo]. More recently, the release of proteins in human [ l l ] and rat [32] pancreatic juice after a single intravenous injection of cholecystokinin-pancreozymin associated with secretin has been found to be nonparallel