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G Rohr

Publications and source records attributed to G Rohr.

At least 55 records · Page 3Linked to original sources
PubMed1987

Evidence in vivo of asynchronous intracellular transport of rat pancreatic secretory proteins.

Labeled proteins which appeared in pancreatic juice after the intravenous (i.v.) injection of [35S]methionine into conscious rats with chronic pancreatic duct fistulae were separated by gel electrophoresis and measured by determination of the radioactivity of each of the separated bands. Radioactivity appeared in the secreted proteins 20 min after injection of the label. In the subsequent 10 min, 6.44% of the radioactivity was found in trypsinogen, whereas 100 min later only 3.4% of the radioactivity was associated with this enzyme. The values at 10 and 100 min for amylase were 10.85% and 21%, respectively, showing an earlier appearance of labeled trypsinogen than of amylase. Chymotrypsinogen behaved similarly to trypsinogen. Early secretion of labeled proteases was also demonstrated by separation of pancreatic proteins by two-dimensional gel electrophoresis followed by fluorography. In pancreatic duct cannulated rats, zymogen granules were prepared 30 and 60 min after injection of the labeled methionine. Determination of the radioactivity of the individual proteins demonstrated a similar time course of the labeling pattern in the zymogen granule fraction to that in pancreatic juice. The results of the experiments suggest an asynchronous secretion of newly synthesized rat pancreatic proteins.

Amylases↗
PubMed1987

Influence of secretagogues on asynchronous secretion of newly synthesized pancreatic proteins in the conscious rat.

The secretion of newly synthesized pancreatic enzymes was studied in pancreatic duct cannulated rats after intravenous injection of 100 microCi of [35S]methionine. Secretion rate was stimulated by intravenous infusion of either cerulein (0.2 microgram/kg h) or carbachol (10 nmol/kg h) starting simultaneously with or 180 min before the injection of the labeled methionine. Secretory proteins were analyzed by sodium dodecyl sulfate (SDS) gel electrophoresis or by nondenaturing gel electrophoresis followed by determination of the radioactivity associated with the individual proteins. Similar to unstimulated controls in all experiments, an early secretion of newly synthesized trypsinogen and chymotrypsinogen was found, whereas amylase and lipase were secreted only after a certain lag period. The results suggest that the intracellular transit of endoproteases is faster than that of other enzymes, irrespective of whether or not secretagogues were applied.

Amylases↗
PubMed1986

Asynchronous secretion of newly synthesized pancreatic proteins in the rat.

The secretion of newly synthesized pancreatic proteins was studied in conscious rats with cannulated pancreatic ducts. Labeled amino acids (3H-leucine and 14C-amino acid mixture) were injected intravenously. The proteins of the pancreatic juice were separated by gel electrophoresis, and the radioactivity in each band was determined. An early secretion of labeled trypsinogen and chymotrypsinogen was found, whereas amylase and lipase were secreted after a certain lag period. In vitro pulse chase experiments showed that amylase was synthesized in the acinar cell but did not move with the same efficacy to the zymogen granules and into the pancreatic juice as proteases.

Amino Acids↗
PubMed1986

Prevention of experimental pancreatitis by somatostatins.

Somatostatin is known to exert a beneficial cytoprotective effect in acute experimental pancreatitis, although it is ineffective regarding mortality in human pancreatitis. The somatostatin analog 008 was found to be more efficient in taurocholate-induced pancreatitis in rats and in ceruletid-induced pancreatitis.

Amylases↗
PubMed1986

Cytoprotective properties of somatostatins.

Secretion of many hormones is inhibited by regular cyclic somatostatin-14. Since additional cytoprotective properties of this hormone have been described, the question arises of whether analogs of somatostatin with increased endocrine activity may also exert increased cytoprotective activity. It could be shown that the endocrine and the cytoprotective property of somatostatin-14 must have different modes of action. In analogs of somatostatin with increased endocrine activity the cytoprotective effect is also increased. A maximal increase in the cytoprotective effect of certain analogs of somatostatin is accompanied by a loss of endocrine activity.

Amino Acid Sequence↗
PubMed1986

Gastric mucosal protection by somatostatins.

Somatostatin and somatostatin derivatives were tested for their ability to prevent gastric hemorrhagic erosions induced by ethanol. The somatostatin analogues were cyclohexapeptides with the rearranged amino acids 7-14 of somatostatin (S-14): Phe-Thr-Lys(Z)-Trp-Phe-D-Pro(I), Phe-Thr-Lys-Trp-Phe-D-Pro(II), Phe-Thr-Lys-D-Trp-Phe-Tyr(III) and Tyr-Phe-D-Trp-Lys-Thr-Phe(IV). In Spraque-Dawley rats receiving ethanol alone, the lesions involved 18.1 +/- 3.2% of the glandular stomach while after S- 14 (10(-7) mol/rat) the lesioned area was reduced to 6.3 +/- 1.1% (p less than 0.05). Peptide I and peptide II (doses 10(-7) -10(-9) mol/rat) decreased the area of erosions to less than 5%. Peptide III was less active and peptide IV was inactive. In rats with chronic gastric fistula S- 14 and peptide II decreased the cysteamine-stimulated acid secretion without affecting the pepsin output. We also continuously measured the intraluminal pH in the stomach of Wistar rats which develop gastric erosions after subcutaneous injection of cysteamine. The erosions were reduced by S- 14 or SMS while the intraluminal pH did not change under the influence of cysteamine or the combination of cysteamine plus S- 14 or SMS. Thus some of the peptides derived from S- 14 exert prominent gastric mucosal protection without influencing gastric secretion.

Animals↗
PubMed1984

An additional secretory protein in the rat pancreas.

An additional protein in rat pancreatic juice has been observed, which is present in healthy rats after pancreatic duct cannulation or in rats in which experimental pancreatitis has been induced by either cerulein or taurocholate. The protein appears 1/2-1 day after surgery or onset of pancreatitis, is present for the following 3-4 days and disappears afterwards. It is found in pancreatic homogenate or in zymogen granules from rats with pancreatitis, but not in normal rats. It does not seem to be related to the recently described 'pancreatic stone protein'. We would like to refer to this protein as 'pancreatitis-associated protein'.

Animals↗
PubMed1983

Effects of in vivo cholinergic stimulation of rat exocrine pancreas.

Peptide and cholinergic secretagogues both produce biphasic dose-response curves for pancreatic enzyme secretion in vitro: supraoptimal doses result in submaximal secretory responses. We compared the effects of maximal and supramaximal doses of a cholinergic agent (carbachol) on rat exocrine pancreas in vivo. In conscious rats, volume and enzyme output were measured from the cannulated pancreatic duct during infusion of carbachol for 3 h. Infusion of 5 X 10(-7) mol . kg-1 . h-1 carbachol caused optimal stimulation, whereas a supraoptimal dose (5 X 10(-6) mol . kg-1 . h-1) resulted in submaximal response. Similar results were achieved when discharge of amylase and protein synthesis was determined in vitro after carbachol in vivo. Supraoptimal doses of carbachol increased serum amylase and enhanced acinar cell lysosomal activity in the Golgi area. The latter appeared to induce fusion of zymogen granules, which resulted in cytoplasmic vacuoles. The in vivo results corroborate in vitro findings of a biphasic dose-response relationship for carbachol and demonstrate destructive effects of supraoptimal concentrations on target cells.

Amylases↗
PubMed1983

Fate of radioactive exocrine pancreatic proteins injected into the blood circulation of the rat. Tissue uptake and transepithelial excretion.

[35S]methionine or [35S]methionine-labeled exocrine pancreatic proteins were injected into the bloodstream of conscious rats. Samples of blood, urine, bile, and pancreatic juice were collected at varying intervals through 7 h. Injection of [35S]methionine resulted in the appearance of trichloroacetic acid--soluble radioactivity [( 35S]methionine) in bile and urine within 4 min and trichloroacetic acid-insoluble radioactivity in blood, bile, and pancreatic juice after 20 min. Analysis of these body fluids by two-dimensional isoelectric focusing/sodium dodecyl sulfate gel electrophoresis and fluorography indicated that rat serum, biliary, and pancreatic proteins were labeled, respectively. After the injection of [35S]methionine-labeled pancreatic proteins, half of the trichloroacetic acid-insoluble radioactivity disappeared from the serum in 10-15 min. Radioactive proteins appeared after 5 min in urine and bile, and, over the course of the experiment, accounted for 1%-2% and 0.3%-0.5% of the injected radioactivity, respectively. Analysis of individual radioactive proteins excreted into bile by two-dimensional isoelectric focusing/sodium dodecyl sulfate gel electrophoresis indicated preferential transhepatic transport of negatively charged pancreatic proteins. The majority of pancreatic proteins (approximately 97%) were taken up by a variety of body tissues, particularly kidney, liver, spleen, and lung. Trichloroacetic acid-soluble radioactivity, largely representing [35S]methionine, appeared sequentially in serum, urine, and bile within 2-12 min. At later experimental time points (greater than 60-90 min), radioactive rat serum, biliary, and pancreatic proteins appeared in blood, bile, and pancreatic juice, respectively. After the injection of 35S-labeled guinea pig pancreatic proteins into the blood circulation of the rat, trichloroacetic acid-insoluble radioactivity, observed in pancreatic juice after 60-90 min, exclusively represented rat exocrine pancreatic proteins as judged by the two-dimensional gel procedure. These studies indicate that pancreatic proteins are removed from the blood circulation by at least three separate pathways: (a) uptake and degradation by a variety of tissues in the body (approximately 97% of injected radioactivity), (b) excretion of intact proteins into urine (1%-2%), and (c) transport of intact proteins into bile (0.3%-0.5%). Transport of exocrine pancreatic proteins from the blood circulation to pancreatic juice could not be demonstrated.

Animals↗
PubMed1982

Alteration of membrane fusion as a cause of acute pancreatitis in the rat.

Infusion of supramaximal doses of cerulein induces acute edematous pancreatitis in the rat. Cannulation of the main pancreatic duct does not prevent the formation of the edema but reveals an almost complete reduction of pancreatic flow. Using freeze-fracture techniques and thin-section electron microscopy, earliest structural alterations were observed at membranes of zymogen granules and the plasma membrane. Fusion of zymogen granules among each other leads to formation of large membrane-bound vacuoles within the cytoplasm. These and individual zymogen granules fuse with the basolateral plasma membrane, discharging their content into the interstitial space. The findings indicate severe changes in the specificity of the intracellular membrane fusion process induced by supramaximal doses of a pancreatic secretagogue, which finally result in autodigestion of the pancreas.

Acute Disease↗
PubMed1982

Prolonged in vivo stimulation of the rat exocrine pancreas by caerulein infusion. Biochemical effects.

Chronic secretory stimulation of the rat exocrine pancreas by continuous infusion of 0.1825 nmol/kg . h caerulein for 4 to 8 days as well as by a dose increased fivefold after the first 3 days of treatment results in three clearly distinct modes of pancreatic reaction apparently independent of the treatment pattern. One group of animals developed degranulation of acinar cells, low enzyme content, and accelerated intracellular transport and discharge of newly synthesized proteins as expected after secretory stimulation. A second group exhibited a striking overgranulation of acinar cells and extremely high enzyme content. In vitro intracellular transport rates were normal and zymogen output per cell in response to caerulein stimulus was elevated. The third group developed apparent desensitization towards hormonal stimulus in vivo. Enzyme content was slightly elevated and secretory behaviour in vitro similar to controls. Basal secretion rates were elevated in most pancreata of all 3 groups, possibly due to persistence of stimulatory effect of caerulein given in vivo up to the moment of sacrifice. Enzyme composition was strikingly changed in favor of the proteases trypsinogen and chymotrypsinogen in all pancreata.

Animals↗