Early Dissociation of Protein Synthesis and Amylase Secretion Following Hormonal Stimulation of the Pancreas

1974 ◽  
Vol 52 (2) ◽  
pp. 198-205 ◽  
Author(s):  
R. Mongeau ◽  
Y. Couture ◽  
J. Dunnigan ◽  
J. Morisset
Keyword(s):  
Protein Synthesis ◽  
Incubation Medium ◽  
Single Injection ◽  
Pancreatic Enzyme ◽  
Amylase Secretion ◽  
Hormonal Stimulation ◽  
Pancreatic Enzyme Secretion ◽  
Metabolic Conditions

The secretion of the various pancreatic enzymes can be increased by hormonal and cholinergic stimulation. However, it is not yet clear among the different investigators if their synthesis remains constant or can be modified according to different metabolic conditions. The secretion and synthesis of the pancreatic proteins were then studied in parallel to evaluate if secretion triggers synthesis or both phenomenons are controlled by separate mechanisms.The approach for these studies consists mainly in a combination of in vivo and in vitro experiments. The stimulants were injected in vivo and the pancreatic secretions were collected for different periods of time. The animals were then sacrificed and protein synthesis was measured in vitro along with the amylase secreted into the incubation medium. The results show that protein synthesis is decreased during the first 15 min after a single injection or infusion of both cholecystokinin–pancreozymin (CCK–PZ) and secretin. This reduction was associated with an increase in amylase secreted into the incubation medium. However, at 30 min after the hormonal stimulation, protein synthesis is increased while secretion into the incubation medium had returned to control levels. This increase in protein synthesis lasts for at least 1 h. These results strongly suggest that pancreatic enzyme secretion and synthesis are dissociated in the early minutes following hormonal stimulation.

Further evidence that protein synthesis can be decreased in vivo following hormonal stimulation in the rat pancreas

1976 ◽  
Vol 54 (3) ◽  
pp. 305-313 ◽  
Author(s):  
R. Mongeau ◽  
J. C. Dagorn ◽  
J. Morisset
Keyword(s):  
Protein Synthesis ◽  
Single Injection ◽  
Protein Biosynthesis ◽  
Specific Radioactivity ◽  
Hormonal Stimulation ◽  
In Vitro System ◽  
Precursor Pool ◽  
Stimulation Of

The present study has been undertaken to determine in the rat the influence of exocrine secretory stimulation on pancreatic protein synthesis. This stimulant consisted of a single injection of cholecystokinin–pancreozymin (8 Ivy units/kg) plus secretin (5 clinical units/kg). The rate of [14C]phenylalanine incorporation into total proteins was measured 5, 11, 17, 30, 45 and 60 min later. Incorporation was significantly decreased after 5 min, then significantly increased at 17 min, and finally returned to control values at 45 min. This biphasic evolution was shown not to be caused by variations in the precursor pool specific radioactivity. We concluded that secretory stimulation of the pancreas can induce a decrease in the rate of protein biosynthesis. This decrease is nevertheless a transient phenomenon, since the rate of biosynthesis was increased at 17 min. These results, obtained from a totally in vivo system, confirm previous data obtained from an in vivo – in vitro system.

Faster protein and ribosome synthesis in thyroxine-induced hypertrophy of rat heart

1985 ◽  
Vol 248 (3) ◽  
pp. C309-C319 ◽  
Author(s):  
D. Siehl ◽  
B. H. Chua ◽  
N. Lautensack-Belser ◽  
H. E. Morgan
Keyword(s):  
Protein Synthesis ◽  
Single Injection ◽  
Plasma Concentrations ◽  
Bicarbonate Buffer ◽  
Ribosomal Subunits ◽  
Ribosome Synthesis ◽  
And Control ◽  
Perfused Hearts

Rates of protein synthesis and degradation were measured in hearts from normal and thyroxine-injected rats that were perfused as working preparations with Krebs-Henseleit bicarbonate buffer containing 400 microU insulin/ml, 2 mM lactate, 10 mM glucose, and normal plasma concentrations of amino acids. Hearts were perfused after four daily injections (1 microgram/g body wt) of thyroxine. Protein synthesis was 24% greater in hypertrophying hearts compared with controls; ribosomal RNA content increased 25%. In addition, the proportion of total RNA in free ribosomal subunits in hypertrophying hearts was unchanged from perfused hearts of control rats and from unperfused normal hearts. These results indicated that increased protein synthetic machinery as monitored by content of ribosomes, rather than more efficient initiation or elongation of peptide chains, accounted for the faster rate of protein synthesis in hypertrophying hearts. Rates of protein degradation were the same in hearts from thyroxine-injected and control animals. When rates of ribosome production were measured in vitro at various times after a single injection of thyroxine in vivo, faster ribosome synthesis was detected within 8 h; no change in the rate of total protein synthesis occurred after a single injection of thyroxine. These studies indicated that accelerated ribosome formation was an early and quantitatively important factor in cardiac hypertrophy.

scholarly journals The control of the form and function of the ribosomes in androgen-dependent tissues by testosterone

1973 ◽  
Vol 134 (3) ◽  
pp. 795-805 ◽  
Author(s):  
W. I. P. Mainwaring ◽  
P. A. Wilce
Keyword(s):  
Protein Synthesis ◽  
Prostate Gland ◽  
Concomitant Administration ◽  
Ventral Prostate ◽  
Hormonal Stimulation ◽  
Pronounced Increase ◽  
Form And Function ◽  
Mandatory Requirement

1. The ribosome content of the rat ventral prostate gland is controlled by the concentrations of circulating androgens and the polyribosomal complement of the total population of ribosomes is acutely dependent on androgenic stimulation. After the administration of testosterone to castrated rats in vivo, there is a pronounced increase in the amounts of heavy (150–240S) polyribosomes. 2. These results are consistent with a pronounced increase in the mRNA and rRNA content of the prostate gland after the administration of testosterone in vivo. 3. From studies conducted both in vitro, the heavy prostate polyribosomes formed after androgenic stimulation are particularly active in protein synthesis. 4. The androgen-stimulated increase in the formation of prostate polyribosomes has a mandatory requirement for sustained RNA and protein synthesis. 5. Since the androgen-mediated increase in prostate polyribosomes may also be suppressed by the concomitant administration of certain anti-androgenic steroids in vivo, the response in polyribosome formation is probably initiated by the binding of a metabolite of testosterone, 5α-dihydrotestosterone, in the prostate gland. 6. The relevance of these findings to the pronounced increase in protein synthesis in androgen-dependent tissues after hormonal stimulation is discussed.

Biochemical Reactions Involved in Pancreatic Enzyme Secretion. I. Activation of the Adenylate Cyclase Complex

1974 ◽  
Vol 52 (2) ◽  
pp. 174-182 ◽  
Author(s):  
A. R. Beaudoin ◽  
C. Marois ◽  
J. Dunnigan ◽  
J. Morisset
Keyword(s):  
Adenylate Cyclase ◽  
Pancreatic Enzyme ◽  
Pancreatic Tissue ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Enzyme Secretion ◽  
Amylase Secretion ◽  
Biochemical Reactions ◽  
Pancreatic Enzyme Secretion

Pancreatic amylase secretion was studied using an in vitro system. Secretion was increased by urecholine and cholecystokinin–pancreozymin (CCK–PZ). Addition of tetracaine and dibucaine to the medium abolished secretion stimulated by urecholine and decreased by 75% that stimulated by CCK–PZ. In contrast, an increase in enzyme secretion was observed after dibutyryl cyclic AMP; this was potentiated by tetracaine added to the medium. Oxygen uptake by pieces of pancreatic tissue was not affected by tetracaine. Adenylate cyclase activity, increased in vitro when CCK–PZ was added to a pancreas homogenate, was inhibited by 15% by tetracaine at 2 mM and by 67.5% at the 10 mM concentration.From data known on biochemical reactions associated with the process of secretion and the results described in the present paper, we propose a model for the activation of the pancreatic adenylate cyclase complex. Associated to the depolarization of the acinar cell plasma membrane by urecholine and CCK–PZ and an inward movement of sodium and calcium, there is an immediate rise in adenylate cyclase activity within 10 s which is timed with the initiation of amylase secretion.

Effect of CCK antagonist L 364718 on meal-induced pancreatic secretion in rats

1990 ◽  
Vol 258 (2) ◽  
pp. G179-G184 ◽  
Author(s):  
M. F. O'Rourke ◽  
R. D. Reidelberger ◽  
T. E. Solomon
Keyword(s):  
Pancreatic Secretion ◽  
Competitive Inhibition ◽  
Pancreatic Enzyme ◽  
Enzyme Secretion ◽  
Amylase Secretion ◽  
Liquid Meal ◽  
Amylase Output ◽  
Pancreatic Enzyme Secretion ◽  
Cck Receptor Antagonist

The specific cholecystokinin (CCK)-receptor antagonist L 364718 was used to examine the role of CCK in meal-induced pancreatic secretion. Unanesthetized rats with gastric, jugular vein, bilepancreatic, and duodenal cannulas were used; bile-pancreatic juice was recirculated. Basal amylase secretion (30% of maximal) was not inhibited by L 364718 doses of 0.5 or 2 mg/kg intravenously. L 364718 (0.02 to 2 mg/kg) caused dose-related inhibition of the maximal amylase response to CCK-8 (200 pmol.kg-1.h-1), with greater than 80% inhibition at doses greater than or equal to 0.5 mg/kg. L 364718 (0.5 mg/kg) shifted the dose-response curve to CCK-8 (25-3,200 pmol.kg-1.h-1) to the right (ED50 increased 10-fold) but did not alter maximal amylase output consistent with competitive inhibition of CCK in vivo. Ingestion of liquid food significantly increased amylase output threefold above basal. L 364718 (0.5 mg/kg) completely blocked this response. These results suggest that although CCK does not regulate basal pancreatic enzyme secretion, it is the primary mediator of pancreatic enzyme secretion in response to a liquid meal.

Pancreatic enzyme secretion: nonspecific stimulation by duodenal mucosal extracts

1981 ◽  
Vol 240 (2) ◽  
pp. G109-G113
Author(s):  
A. La Bella ◽  
R. G. Lahaie ◽  
H. Sarles ◽  
J. C. Dagorn
Keyword(s):  
Pancreatic Enzyme ◽  
Extraction Procedure ◽  
Pancreatic Enzymes ◽  
Enzyme Secretion ◽  
Specific Enzyme ◽  
Pancreatic Enzyme Secretion ◽  
Related Enzyme

Felber et al. (Lancet 2: 185-188, 1974) reported that duodenal extracts obtained from rats fed a given meal induced the specific secretion of related pancreatic enzymes. Such an observation challenges the generally accepted theory of parallel secretion of pancreatic enzymes. Although these experiments were faithfully reproduced, no induction of specific enzyme secretion could be obtained. Moreover, comparison of the secretagogue potency of different preparations of duodenal extract, both in vivo (anesthetized rat) and in vitro (pancreatic lobules), demonstrated that in the original extraction procedure most of the secretagogue activity was lost. Finally, even the fully active extract failed to induce specific enzyme secretion. It is therefore unlikely that duodenal extracts from rats fed a specific meal can induce selective secretion of the related enzyme.

IN VITRO UPTAKE OF TRITIATED OESTRADIOL BY THE ANTERIOR HYPOTHALAMUS AND HYPOPHYSIS OF THE RAT

1970 ◽  
Vol 64 (4) ◽  
pp. 687-695 ◽  
Author(s):  
Junzo Kato
Keyword(s):  
Incubation Medium ◽  
Posterior Hypothalamus ◽  
Anterior Hypothalamus ◽  
Ovariectomized Rats ◽  
Free Medium ◽  
Cortex Cerebri ◽  
Anterior Hypophysis ◽  
In Vitro Uptake

ABSTRACT The anterior, middle, and posterior hypothalamus, the cortex cerebri, the anterior hypophysis as well as the diaphragm of adult ovariectomized rats were incubated in vitro with tritiated 17β-oestradiol. The uptake of tritiated oestradiol was differentially distributed intracerebrally with higher accumulation in the anterior hypothalamus and the hypophysis. Lowering the temperature of the incubation medium caused a reduction in the uptake of radioactivity by the anterior hypothalamus as compared to that found in other brain tissues. Tritiated oestradiol taken up in vitro by the anterior hypothalamus and the hypophysis tended to be retained after further incubation in a steroid-free medium. The addition of non-radioactive 17β-oestradiol to the medium inhibited the uptake of tritiated oestradiol by these tissues. Moreover, pretreatment with non-radioactive 17β-oestradiol in vivo prevented the preferential accumulation of tritiated oestradiol in vitro in the anterior hypothalamus and the hypophysis. These results indicate that oestradiol is preferentially taken up in vitro by the anterior hypothalamus and the hypophysis of the rat.

Effect of microbial isolates on microbial yield estimation in RUSITEC system

1998 ◽  
Vol 22 ◽  
pp. 306-308
Author(s):  
M. D. Carro ◽  
E. L. Miller
Keyword(s):  
Protein Synthesis ◽  
Liquid Phase ◽  
Solid Phase ◽  
Liquid Fraction ◽  
Microbial Protein ◽  
Microbial Protein Synthesis ◽  
Continuous Culture System ◽  
The One

The estimation of rumen microbial protein synthesis is one of the main points in the nitrogen (N)-rationing systems for ruminants, as microbial protein provides proportionately 0.4 to 0.9 of amino acids entering the small intestine in ruminants receiving conventional diets (Russell et al., 1992). Methods of estimating microbial protein synthesis rely on marker techniques in which a particular microbial constituent is related to the microbial N content. Marker : N values have generally been established in mixed bacteria isolated from the liquid fraction of rumen digesta and it has been assumed that the same relationship holds in the total population leaving the rumen (Merry and McAllan, 1983). However, several studies have demonstrated differences in composition between solid-associated (SAB) and fluid-associated bacteria in vivo (Legay-Carmier and Bauchart, 1989) and in vitro (Molina Alcaide et al, 1996), as well in marker : N values (Pérez et al., 1996). This problem could be more pronounced in the in vitro semi-continuous culture system RUSITEC, in which there are three well defined components (a free liquid phase, a liquid phase associated with the solid phase and a solid phase), each one having associated microbial populations.The objective of this experiment was to investigate the effect of using different bacterial isolates (BI) on the estimation of microbial production of four different diets in RUSITEC (Czerkawski and Breckenridge, 1977), using (15NH4)2 SO4 as microbial marker, and to assess what effects any differences would have on the comparison of microbial protein synthesis between diets.This study was conducted in conjunction with an in vitro experiment described by Carro and Miller (1997). Two 14-day incubation trials were carried out with the rumen simulation technique RUSITEC (Czerkawski and Breckenridge, 1977). The general incubation procedure was the one described by Czerkawski and Breckenridge (1977) and more details about the procedures of this experiment are given elsewhere (Carro and Miller, 1997).

scholarly journals Phosphorylation of eukaryotic initiation factor 4E (eIF4E) at Ser209 is not required for protein synthesis in vitro and in vivo

2001 ◽  
Vol 268 (20) ◽  
pp. 5375-5385 ◽  
Author(s):  
Linda McKendrick ◽  
Simon J. Morley ◽  
Virginia M. Pain ◽  
Rosemary Jagus ◽  
Bhavesh Joshi
Keyword(s):  
Protein Synthesis ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Eukaryotic Initiation Factor 4E
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