Regulation of intestinal cholecystokinin and somatostatin mRNA by bombesin in rats

1991 ◽  
Vol 261 (1) ◽  
pp. G71-G77 ◽  
Author(s):  
S. Kanayama ◽  
R. A. Liddle
Keyword(s):  
Steady State ◽  
Effective Dose ◽  
Trypsin Inhibitor ◽  
Gastrointestinal Hormones ◽  
Soybean Trypsin Inhibitor ◽  
Mrna Levels ◽  
Intravenous Infusions ◽  
Basal Plasma ◽  
Stimulation Of ◽  
Cck Release

The neuropeptide bombesin has been shown to stimulate secretion of several gastrointestinal hormones, including cholecystokinin (CCK). We have previously demonstrated that stimulation of CCK release by feeding is associated with an increase in steady-state intestinal CCK mRNA levels. The purpose of the present study was to determine whether bombesin stimulates CCK release in rats and, if so, to determine whether bombesin regulates CCK mRNA levels in a manner similar to that of feeding. To establish a proper dose of bombesin for stimulating CCK release, rats received 1-h intravenous infusions of 0.25, 1, 4, or 16 micrograms.kg-1.h-1 bombesin. Basal plasma CCK levels averaged 1.8 +/- 0.4 pM and increased to peak levels of 2.9 +/- 0.6 pM within 15 min of infusion with 4 micrograms.kg-1.h-1 bombesin (the maximally effective dose). With the use of this dose, rats then received infusions of bombesin or saline lasting up to 24 h. At 1, 2, 4, and 24 h, animals were killed for collection of plasma for CCK measurements and of intestine for measurements of intestinal CCK and somatostatin mRNA levels. Bombesin treatment stimulated an increase in plasma CCK levels at 1 h, but levels declined to basal by 4 h, where they remained at 24 h. Despite increasing plasma CCK levels, bombesin infusion, unlike dietary stimulation, had no effect on duodenal CCK mRNA levels. Finally, to determine whether the decrease in plasma CCK levels after prolonged bombesin treatment was due to tachyphylaxis, rats treated with bombesin for 4 h were also fed soybean trypsin inhibitor (a known stimulus of CCK secretion).(ABSTRACT TRUNCATED AT 250 WORDS)

Role of PKCα in feedback regulation of Na+transport in an electrically tight epithelium

2002 ◽  
Vol 283 (4) ◽  
pp. C1122-C1132 ◽  
Author(s):  
Mouhamed S. Awayda ◽  
Justin D. Platzer ◽  
Roxanne L. Reger ◽  
Abderrahmane Bengrine
Keyword(s):  
Steady State ◽  
Blot Analysis ◽  
Feedback Regulation ◽  
Feedback Mechanism ◽  
Mrna Levels ◽  
Protein Levels ◽  
Pkc Isoforms ◽  
A6 Epithelia ◽  
Tight Epithelia ◽  
Stimulation Of

It has long been known that Na+ channels in electrically tight epithelia are regulated by homeostatic mechanisms that maintain a steady state and allow new levels of transport to be sustained in hormonally challenged cells. Little is known about the potential pathways involved in these processes. In addition to short-term effect, recent evidence also indicates the involvement of PKC in the long-term regulation of the epithelial Na+ channel (ENaC) at the protein level (40). To determine whether stimulation of ENaC involves feedback regulation of PKC levels, we utilized Western blot analysis to determine the distribution of PKC isoforms in polarized A6 epithelia. We found the presence of PKC isoforms in the conventional (α and γ), novel (δ, η, and ε), and atypical (ι, λ, and ζ) groups. Steady-state stimulation of Na+ transport with aldosterone was accompanied by a specific decrease of PKCα protein levels in both the cytoplasmic and membrane fractions. Similarly, overnight treatment with an uncharged amiloride analog (CDPC), a procedure that through feedback regulation causes a stimulation of Na+ transport, also decreased PKCα levels. These effects were additive, indicating separate mechanisms that converge at the level of PKCα. These effects were not accompanied by changes of PKCα mRNA levels as determined by Northern blot analysis. We propose that this may represent a novel regulatory feedback mechanism necessary for sustaining an increase of Na+ transport.

Modulation of human DNA methyltransferase activity and mRNA levels in the monoblast cell line U937 induced to differentiate with dibutyryl cyclic AMP and phorbol ester

1993 ◽  
Vol 11 (2) ◽  
pp. 191-200 ◽  
Author(s):  
P Soultanas ◽  
P D Andrews ◽  
D R Burton ◽  
D P Hornby
Keyword(s):  
Steady State ◽  
Cyclic Amp ◽  
Gene Transcription ◽  
Phorbol Ester ◽  
Specific Activity ◽  
Mrna Levels ◽  
Dibutyryl Cyclic Amp ◽  
Nuclear Extracts ◽  
Steady State Levels ◽  
Stimulation Of

ABSTRACT The regulation of DNA (cytosine-5) methyltransferase (DNA MeTase) enzyme activity and gene expression was examined in the monoblastoid U937 cell line induced to differentiate with either dibutyryl cyclic AMP (dbcAMP) or phorbol ester. dbcAMP treatment was found to cause the rapid (<4 h) suppression of DNA MeTase specific activity, with no DNA MeTase activity detectable after 10 h. Equally, no DNA MeTase activity was detectable in nuclear extracts of fresh peripheral blood monocytes. Using both a U937 DNA MeTase cDNA and a mouse DNA MeTase cDNA as probes, steady-state levels of DNA MeTase mRNA were found to decline sharply between 4 and 15 h after dbcAMP treatment. No DNA MeTase mRNA was detectable after 20 h of dbcAMP treatment. Nuclear run-on analysis showed there to be only a small (40%) suppression of DNA MeTase gene transcription in cells treated with dbcAMP for 24 h, implying a role for post-transcriptional processes in the regulation of DNA MeTase mRNA levels. The observed decline in DNA MeTase activity/mRNA levels appeared to precede the dbcAMP-induced arrest in DNA replication, as judged by the incorporation of tritiated thymidine into DNA. In contrast to the effect of dbcAMP, treatment of U937 cells with the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA) led to an overall stimulation of DNA MeTase specific activity. The TPA response was found to be complex and broadly consisted of an early (0–15 h) burst of DNA MeTase activity followed by a more gradual sustained increase in DNA MeTase activity after prolonged (16–40 h) TPA treatment. The early phase of high DNA MeTase activity was not mirrored by an increase in steady-state levels of DNA MeTase mRNA, as judged by Northern blot analysis. However, a substantial induction of DNA MeTase mRNA levels was observed after 20–24 h of TPA treatment. Nuclear run-on analysis showed this not to be due to any significant increase in DNA MeTase gene transcription. The observed increases in DNA MeTase activity/mRNA levels were observed whilst cells were undergoing deproliferation. Interestingly, the addition of TPA and more physiological protein kinase C (PKC) activators, such as diacylglycerol and phosphatidylserine, to DNA MeTase-enriched nuclear extracts generated a 4·5-fold and a 1·5-fold increase in DNA MeTase specific activity respectively. The TPA-induced stimulation of DNA MeTase activity could be inhibited by the PKC inhibitor H-9, implicating a role for PKC in the regulation of DNA MeTase activity in vivo.

CCK, bombesin, and carbachol stimulate c-fos, c-jun, and c-myc oncogene expression in rat pancreatic acini

1992 ◽  
Vol 263 (3) ◽  
pp. G327-G332 ◽  
Author(s):  
L. Lu ◽  
C. D. Logsdon
Keyword(s):  
Mrna Expression ◽  
Gastrointestinal Hormones ◽  
Mrna Levels ◽  
Pancreatic Acini ◽  
Myc Oncogene ◽  
Maximal Stimulation ◽  
High Affinity Site ◽  
Oncogene Activation ◽  
Stimulation Of

To identify possible nuclear signals mediating long-term regulation of the pancreas by gastrointestinal hormones, the expression of c-fos, c-jun, and c-myc was investigated in rat pancreatic acini. Stimulation of the acini with cholecystokinin octapeptide (CCK-8, 100 pM), bombesin (10 nM), or carbachol (10 microM), but not gastrin (100 nM), secretin (100 nM), or vasoactive intestinal peptide (10 nM) induced an increase in oncogene mRNA expression. The percent increases of c-fos, c-jun, and c-myc mRNA were 207 +/- 40, 171 +/- 26, and 46 +/- 19 (n = 5) for CCK-8; 223 +/- 71, 159 +/- 31, and 43 +/- 21 (n = 5) for bombesin; and 125 +/- 51, 123 +/- 58, and 67 +/- 19 (n = 5) for carbachol, respectively. CCK-induced increases in oncogene mRNA were rapid and transient. c-fos and c-jun mRNA levels were increased after 30 min stimulation, peaked at 1 h, and returned to basal level in 2 h. Activation of c-myc was more prolonged with levels remaining elevated for at least 3 h. The effects of CCK-8 were concentration dependent. Detectable stimulation was seen at 10 pM; maximal stimulation occurred at 10 nM and was not affected by further increase in the concentration of CCK-8. JMV-180, a high-affinity site CCK receptor agonist and low-affinity site antagonist, alone did not stimulate c-fos mRNA expression but inhibited c-fos mRNA expression induced by CCK-8. These results suggest that the interaction between CCK and the low-affinity state of the CCK receptor is responsible for oncogene activation.

scholarly journals Stimulatory Effect of Phenylmethylsulfonyl Fluoride upon Sulfate Uptake by Costal Cartilage

1983 ◽  
Vol 36 (1) ◽  
pp. 35 ◽  
Author(s):  
NeiI M McKern
Keyword(s):  
Sodium Fluoride ◽  
Trypsin Inhibitor ◽  
Incubation Medium ◽  
Costal Cartilage ◽  
Soybean Trypsin Inhibitor ◽  
Similar Degree ◽  
Phenylmethylsulfonyl Fluoride ◽  
Sulfate Uptake ◽  
Metabolic Processes ◽  
Stimulation Of

Uptake of [35Slsulfate by segments of rat costal cartilage during culture was greatly stimulated when freshly prepared phenylmethylsulfonyl fluoride or diisopropylfluorophosphate was included in the incubation medium. By contrast, hydrolysed diisopropylfluorophosphate, sodium fluoride or soybean trypsin inhibitor did not stimulate [35Slsulfate uptake. Incorporation of four other radioactive precursors of cartilage synthesis was almost completely suppressed during cartilage incubation in the presence of phenylmethylsulfonyl fluoride. However, stimulation of [3SSlsulfate binding by the latter was shown to occur at sites other than on glycosaminoglycan molecules and to a similar degree with both active and inactivated cartilage. These and other data indicate that the stimulatory effect of phenylmethylsulfonyl fluoride on [3sSlsulfate uptake is independent of normal metabolic processes, and may involve the binding of phenylmethylsulfonyl fluoride to cartilage proteins.

Pancreatic digestive enzyme gene expression: effects of CCK and soybean trypsin inhibitor

1989 ◽  
Vol 256 (4) ◽  
pp. G733-G738 ◽  
Author(s):  
S. Rosewicz ◽  
L. D. Lewis ◽  
X. Y. Wang ◽  
R. A. Liddle ◽  
C. D. Logsdon
Keyword(s):  
Gene Expression ◽  
Trypsin Inhibitor ◽  
Intravenous Infusion ◽  
Digestive Enzyme ◽  
Plasma Concentrations ◽  
Soybean Trypsin Inhibitor ◽  
Mrna Levels ◽  
Enzyme Gene ◽  
Cloned Cdna ◽  
Cck Receptor Antagonist

Regulation of pancreatic gene expression by cholecystokinin (CCK) was examined in the rat using cloned cDNA probes to quantify changes in specific mRNAs (amylase, trypsinogen I, chymotrypsinogen B, and ribonuclease). Rats were administered intraduodenally an elemental liquid diet. Plasma CCK levels were raised to levels comparable to physiological postprandial levels either by intraduodenal perfusion with soybean trypsin inhibitor (SBTI) (6.9 +/- 1.0 pM, n = 8) or by continuous intravenous infusion with cholecystokinin octapeptide (CCK-8, 6.0 +/- 0.9 pM, n = 6). SBTI infusion resulted in fivefold increases in trypsinogen I and chymotrypsinogen B mRNA levels after 48 h. In contrast SBTI infusion had no effect on amylase mRNA levels and led to a decrease in ribonuclease mRNA levels to approximately 50% of control after 48 h. Intravenous infusion with CCK-8 for 24 h resulted in plasma levels of CCK comparable to those obtained with SBTI and had similar effects on digestive enzyme mRNA levels. These data suggested that SBTI acted via its ability to raise plasma CCK levels. To further test the specificity of these effects, animals were infused intraduodenally with the specific CCK receptor antagonist L364,718. Although the antagonist itself had no effect on digestive enzyme mRNA levels, antagonist treatment totally abolished the effects of both CCK infusion and SBTI treatment. These data therefore indicate that CCK regulates digestive enzyme gene expression at plasma concentrations comparable to physiological postprandial levels. Furthermore, the ability of SBTI infusion to increase plasma CCK accounts for its effects on pancreatic digestive enzyme mRNA levels.

Effect of omeprazole on gene expression in canine gastric parietal cells

1991 ◽  
Vol 260 (3) ◽  
pp. G434-G439 ◽  
Author(s):  
V. W. Campbell ◽  
T. Yamada
Keyword(s):  
Gene Expression ◽  
Steady State ◽  
Acid Secretion ◽  
Parietal Cells ◽  
Mrna Levels ◽  
Coordinate Expression ◽  
Beta Actin ◽  
Steady State Levels ◽  
Gastric Parietal Cells ◽  
Stimulation Of

Stimulation of gastric parietal cells by carbachol induces coordinate expression of the genes for two enzymes involved in the process of acid secretion, H(+)-K(+)-ATPase and carbonic anhydrase II (CA II). The basis of this coordinate expression was examined in experiments using parietal cells that had been pretreated with omeprazole. We observed a twofold increase in the steady-state mRNA levels of both H(+)-K(+)-ATPase and CA II after cells were treated with the inhibitor. The induction of CA II mRNA by carbachol followed the same kinetics in omeprazole-pretreated cells as in those that were not pretreated, suggesting that the induction of CA II gene expression by carbachol was not dependent on activation of the gastric H(+)-K(+)-ATPase. In addition, carbachol stimulation of omeprazole-pretreated cells resulted in an induction of one or more larger mRNA species that hybridized with the H(+)-K(+)-ATPase probe. The observation that carbachol-induced increases in steady-state levels of beta-actin mRNA in parietal cells could be inhibited by omeprazole pretreatment suggests a possible linkage between increased beta-actin gene expression and the process of acid secretion.

Somatostatin regulates duodenal cholecystokinin and somatostatin messenger RNA

1990 ◽  
Vol 258 (3) ◽  
pp. G358-G364 ◽  
Author(s):  
S. Kanayama ◽  
R. A. Liddle
Keyword(s):  
Trypsin Inhibitor ◽  
Messenger Rna ◽  
Endocrine Cells ◽  
Elemental Diet ◽  
Fold Increase ◽  
Mrna Levels ◽  
Experimental Conditions ◽  
Gastrointestinal Peptides ◽  
Somatostatin 14 ◽  
Cck Release

The gastrointestinal peptides, cholecystokinin (CCK) and somatostatin, are produced by discrete endocrine cells in the mucosa of the small intestine. Although somatostatin may inhibit CCK secretion, the mechanism by which this occurs is unknown. The present study was designed to determine the effect of somatostatin on intestinal CCK and somatostatin mRNA levels. Rats, prepared with indwelling intraduodenal and jugular cannulas, were first fed an elemental diet that did not stimulate CCK release. Next, as a means of stimulating CCK secretion, soybean trypsin inhibitor was added to the diet and perfused intraduodenally at 50 mg/h for 24 h. Trypsin inhibitor caused an 11-fold increase in plasma CCK levels and a 2.4-fold increase in duodenal CCK mRNA levels. Simultaneous intravenous infusion of somatostatin-14 (1-100 micrograms.kg-1.h-1) reduced trypsin inhibitor-stimulated CCK levels by 50% and lowered trypsin inhibitor-stimulated CCK mRNA levels by 58%. Somatostatin infusion also reduced intestinal somatostatin mRNA levels stimulated by trypsin inhibitor but did not affect basal somatostatin mRNA levels. Duodenal CCK and somatostatin peptide concentrations did not change under any of the experimental conditions. These studies demonstrate that somatostatin reduces duodenal CCK mRNA levels stimulated by diet and suggest that somatostatin itself inhibits duodenal somatostatin gene expression.

Mechanisms of inactivation of the action of aldosterone on collecting duct by TGF-β

2000 ◽  
Vol 278 (3) ◽  
pp. F425-F433 ◽  
Author(s):  
Russell F. Husted ◽  
Rita D. Sigmund ◽  
John B. Stokes
Keyword(s):  
Steady State ◽  
Transforming Growth Factor ◽  
Collecting Duct ◽  
Transforming Growth Factor Β ◽  
Mrna Levels ◽  
Α Subunit ◽  
Pump Activity ◽  
Steady State Levels ◽  
Medullary Collecting Duct ◽  
Stimulation Of

The purpose of these experiments was to investigate the mechanisms whereby transforming growth factor-β (TGF-β) antagonizes the action of adrenocorticoid hormones on Na+ transport by the rat inner medullary collecting duct in primary culture. Steroid hormones 1) increased Na+ transport by three- to fourfold, 2) increased the maximum capacity of the Na+-K+ pump by 30–50%, 3) increased the steady-state levels of the α1-subunit of the Na+-K+-ATPase by ∼30%, and 4) increased the steady-state levels of the α-subunit of the rat epithelial Na+ channel (α-rENaC) by nearly fourfold. TGF-β blocked the effects of steroids on the increase in Na+ transport and the stimulation of the Na+-K+-ATPase and pump capacity. However, there was no effect of TGF-β on the steroid-induced increase in mRNA levels of α-rENaC. The effects of TGF-β were not secondary to the decrease in Na+ transport per se, inasmuch as benzamil inhibited the increase in Na+ transport but did not block the increase in pump capacity or Na+-K+-ATPase mRNA. The results indicate that TGF-β does not inactivate the steroid receptor or its translocation to the nucleus. Rather, they indicate complex pathways involving interruption of the enhancement of pump activity and activation/inactivation of pathways distal to the steroid-induced increase in the transcription of α-rENaC.

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