Energy sources for protein synthesis and enzymatic secretion in rat pancreas in vitro

Bauduin, H; Colin, Martine; Dumont, Jacques Emile

doi:10.1016/0005-2787(69)90301-3

Cited by 74 publications

(27 citation statements)

References 32 publications

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“…In contrast Bauduin et al (24,25) found that while incorporation of L-[4,5-3H]-leucine in vitro into rat pancreas was linear for less than 20 min at a concentration of 26 p M leucine, it was linear for 2 h at a concentration of 0.8 mM. We incubated our minces in the presence of 1 mM leucine.…”

Section: Discussionmentioning

confidence: 63%

DNA and Protein Synthesis in Developing Rat Pancreas

et al. 1987

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ABSTRACT. To define developmental patterns, we determined the rate of protein and DNA synthesis in rat pancreas at birth, 1, 2, 3, 7, 10, 14, 21, 28 days, 2 months, 3 months, and in adults. Fragments of freshly minced pancreas were incubated with [3H]-thymidine and [14Cj-leucine and the DNA and protein synthesis rates were measured. We found that 1) DNA content was lowest at birth, rose through day 3, plateaued at about 8 mg/g wet weight through day 14, then slowly decreased to the adult value of about 5 mg/g at 2 months; 2) protein content, although high at birth, decreased rapidly to a value of 80 mg/g at day 3 and slowly rose to the adult value of 160 mglg; 3) protein synthesis, low at birth, rapidly increased to about five times the adult value by day 3, and remained elevated for the 1st month; 4) DNA synthesis was 15 times the adult rate at birth, increased to 30 times at 3 days of age, then declined slowly in an exponential fashion to the adult value. We conclude that the pancreas at birth is poised biosynthetically to undergo a rapid hyperplastic and hypertrophic response, and this process reaches a maximal rate at about 3 days of age. (Pediatr Res 22: 34-38,1987) Abbreviations MEM, minimum essential medium BSA, bovine serum albumin SA, specific activity PCA, perchloric acid CCK, cholecystokinin Numerous studies have defined the structural and functional development of rodent exocrine pancreas. Similarly, a number of studies has evaluated the effects of various agents thought to be trophic for the exocrine pancreas on DNA and protein content of the developing pancreas. Previous studies, however, have evaluated total DNA and protein content, but not actual rates of synthesis of DNA and protein at various ages (1-5). Since cellular content of biomolecules reflects the opposing actions of synthesis and degradation, the true effects of any agent tested may be masked when total organ content is measured. In addition, increases in DNA synthesis in the stomach and small intestine can be observed before an increase in DNA content itself (6). A further difficulty is that technically it is extremely difficult to remove the entire pancreas from neonatal rats. Accordingly, we have evaluated DNA and protein synthesis in rat pancreas of various ages and compared synthetic rates to those found in the adult animal. Not surprisingly, the synthesis rates of both were found to be considerably higher in the immature animal than in the mature animal. MATERIALS AND METHODSSprague Dawley rats obtained from King Laboratories, Madison, WI were used for all studies and were kept under controlled light and temperature conditions. After birth, the rats were not disturbed except for the addition of food and water. Pups were sacrificed at the stated ages a 2 h for ages up to 72 h, and a 1 day for ages 1 to 4 wk. Adult animals (males only) were 4-6 months old. The date of birth was designated as day 0. Before weaning, rats were not fasted; after weaning (day 21), rats were fasted overnight before sacrifice, but allowed free access t...

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Section: Discussionmentioning

confidence: 63%

DNA and Protein Synthesis in Developing Rat Pancreas

et al. 1987

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“…Therefore the NAD content of parotid mitochondria prepared under various conditions was determined ( [4,22,23] in its slow glycolytic activity but differs from these latter tissues in its inability to increase glucose utilization and lactic acid production under anaerobic conditions. It can therefore be assumed that in the parotid gland glucose or endogenous glycogen cannot serve efficiently as an energy source.…”

Section: Calcium Concentration In the Gland And Its Effect On Respiramentioning

confidence: 99%

Energy Production in Rat Parotid Gland

Feinstein

Schramm

1970

European Journal of Biochemistry

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Rat parotid gland slices showed a very slow rate of glucose utilization and lactic acid produca tion, both in the presence and in the absence of oxygen. Epinephrine. which caused rapid enzyme secretion by the slices did not affect the low rate of glycolysis.A rough calculation indicates that in the parotid gland ATP is produced by oxidative phosphorylation 50 times faster than by glycolysis. The mitochondria, when isolated and tested in presence of EDTA or EGTA showed respiratory activity and respiratory control comparable to those of liver mitochondria. Adenosine 3' : 6'-cyclic phosphate, which is an intermediate in induction of enzyme secretion, showed no clear-cut effect on the functions of the parotid mitochondria. Isolation of the mitochondria in the absence of the above chelators yielded a preparation which was almost depleted of NAD, respired feebly on NAD linked substrates and showrd no respiratory control. Addition of NADf restored respiration. The damage caused to these mitochondria during isolation was attributed to the high calcium concentrations found in the gland. Addition of small amounts of free calcium to functional parotid mitochondria indeed caused the loss of NAD and the decline of respiration. Tested in parallel experiments, liver mitochondria were much more resistant t o added calcium. Their initial calcium content was one tenth that of the parotid mitochondria. The control of calcium distribution in the parotid gland and the possible functions of calcium are discussed.Previous work showed that adenosine 3' : 5' cyclic phosphate (Ado-3' : 5'-P) is a n intermediate in the induction of enzyme secretion in rat parotid gland [l]. It had also been found that the secretion process in exocrine glands is critically dependent on energy [2-41. It therefore seemed possible that Ado-3': 5'-P controls the secretion process by acting on a step of energy supply. Since there is little information on the energy producing systems of exocrine glands it was decided t o investigate these systems in some detail. It will be shown in the present work that the glycolytic activity of the parotid gland is very poor and therefore probably unable to produce enough ATP for secretion. On the other hand, the mitochondria contained efficient ATP producing systems which were unaffected by Ado-3':5'-P. Calcium which was found in very high concentration in the gland seemed t o cause, in the absence of EDTA, extensive damage to the mitochondria, including depletion of NAD. MATERIALS ASD METHODS Rat Parotid Slices SystemExperiments were carried out according t o the procedure previously used [3]. At the beginning and termination of the experiments relevant analyses were performed on slices and on incubation medium. Isolation of a Mitochondria1 Fraction from Parotid GlandAll manipulations were carried out a t 0"-4". Glands were collected in 0.25 M sucrose adjusted to pH 7.5 with sodium bicarbonate. A homogenate was prepared in sucrose medium (0.25 M sucrose, 0.5 mM EDTA and 0.5 mM EGTA, pH 7.5). Sucrose medium with I mM EDTA wi...

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“…Antimycin-A (10-5 M) and dinitrophenol (10-3 M) increased basal secretion by 46 and 40 % respectively whereas stimulation of secretion by ionophores was abolished. Bauduin, Colin & Dumont (1969) Li Ringer Ca2+-free (4) 8-82 ± 045 8-63 ± 0-65 8-71 ± 036 Rat pancreas fragments were preincubated and incubated in appropriate media as described in methods. Amylase in the media was assayed by Bernfeld (1955) method and expressed as % of total amylase in the medium + S.E.…”

Section: Stimulus-secretion Coupling In Rat Pancreasmentioning

confidence: 99%

Stimulus‐secretion coupling in rat pancreas: role of sodium, calcium and cyclic nucleotides studied by X‐537A and BrX‐537A.

Singh¹

1980

The Journal of Physiology

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SUMMARY1. The aim of the present work was to study the role of Na+, Ca2+ and cyclic nucleotides in stimulus-secretion coupling in rat pancreatic acinar cells utilizing Ca2+ specific ionophore A23187 as well as ionophores X-537A and BrX-537A which transport both monovalent and divalent cations across biological membranes.2. X-537A, BrX-537A and A23187 increased amylase secretion by a direct energy dependent action without damaging the cells. Antimycin-A and dinitrophenol increased the spontaneous release of amylase.3. In the absence of extracellular Ca2+, the secretary response to X-537A and BrX-537A was reduced by 57 and 50 % respectively whereas A23187 was without effect. In the absence of extracellular Na+, both basal and ionophore stimulated secretion of amylase were increased. Replacement of Na+ by Li+ or Tris+ in Ca2+-free medium abolished the increase in amylase secretion.4. X-537A increased bidirectional flux of uCa2+. Efflux of 45Ca2+ persisted in Ca2+-free media. In Tris-Ringer and Li-Ringer, basal 45Ca2+ influx and amylase secretion were increased. Moreover X-537A enhanced both 45Ca2+ efflux and amylase secretion. This effect was abolished in media containing no Na+ and Ca2+ suggesting that Na+ concentration gradient across the membrane is critical for digestive enzyme secretion.5. Theophylline increased basal concentration of cyclic-GMP at 1, 2, 5, 15 and 30 min. X-537A stimulated cyclic-GMP synthesis in presence of theophylline with a peak effect observed at 15 min with X-537A. Incubation of pancreatic fragments in Ca2+-free media containing EGTA (5 x 10-5 M) decreased basal and X-537A stimulated synthesis of cyclic-GMP.6. From these data it is concluded that Na+ plays a direct role in Ca2+ mobilization and exocytosis. Like other tissues, cyclic-GMP synthesis is dependent on extracellular Ca2+ and does not seem to play a role in stimulus-secretion coupling.

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Energy sources for protein synthesis and enzymatic secretion in rat pancreas in vitro

Cited by 74 publications

References 32 publications

DNA and Protein Synthesis in Developing Rat Pancreas

DNA and Protein Synthesis in Developing Rat Pancreas

Energy Production in Rat Parotid Gland

Stimulus‐secretion coupling in rat pancreas: role of sodium, calcium and cyclic nucleotides studied by X‐537A and BrX‐537A.

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