Contractile protein synthesis rates in vivo in the rat jejunum: modulating role of adrenalectomy and thyroidectomy on ethanol-induced changes

The ability of chloroplasts isolated from Acetabulana mediterranea to synthesize the protein amino acids has been investigated. When this chloroplast isolate was presented with 14CO2 for periods of 6–8 hr, tracer was found in essentially all amino acid species of their hydrolyzed protein Phenylalanine labeling was not detected, probably due to technical problems, and hydroxyproline labeling was not tested for The incorporation of 14CO2 into the amino acids is driven by light and, as indicated by the amount of radioactivity lost during ninhydrin decarboxylation on the chromatograms, the amino acids appear to be uniformly labeled. The amino acid labeling pattern of the isolate is similar to that found in plastids labeled with 14CO2 in vivo. The chloroplast isolate did not utilize detectable amounts of externally supplied amino acids in light or, with added adenosine triphosphate (ATP), in darkness. It is concluded that these chloroplasts are a tight cytoplasmic compartment that is independent in supplying the amino acids used for its own protein synthesis. These results are discussed in terms of the role of contaminants in the observed synthesis, the "normalcy" of Acetabularia chloroplasts, the synthetic pathways for amino acids in plastids, and the implications of these observations for cell compartmentation and chloroplast autonomy.

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Role of endothelial cells in regulating hemoglobin-induced changes in lymphatic pumping

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1992.263.6.h1880 ◽

1992 ◽

Vol 263 (6) ◽

pp. H1880-H1887 ◽

Cited By ~ 1

Author(s):

R. M. Elias ◽

J. Eisenhoffer ◽

M. G. Johnston

Keyword(s):

Endothelial Cells ◽

Smooth Muscle ◽

Inhibitory Effect ◽

Direct Inhibitory Effect ◽

Induced Changes ◽

Lymphatic Pumping ◽

Pumping Activity

Studies with a sheep isolated duct preparation in vivo demonstrated that the route of administration of hemoglobin was important in demonstrating its inhibitory effect on lymphatic pumping. With autologous oxyhemoglobin administered intravenously (final plasma concentration 5 x 10(-5) M), pumping was not inhibited. However, the addition of oxyhemoglobin (5 x 10(-5) M) into the reservoir (lumen of the duct) resulted in > 95% inhibition of pumping. The extraluminal administration of oxyhemoglobin (10(-5) M) to bovine mesenteric lymphatics in vitro resulted in a 40% inhibition of pumping, whereas the introduction of oxyhemoglobin (10(-5) M) into the lumen of the vessels suppressed pumping 95%. In vessels mechanically denuded of endothelium, intraluminal oxyhemoglobin inhibited pumping 50%. These results suggested that oxyhemoglobin depressed pumping through an effect on both smooth muscle and endothelium. Once pumping was inhibited with oxyhemoglobin administration, stimulation of the duct with elevations in transmural pressure restored pumping activity when endothelial cells were present. However, in the absence of endothelium, pumping decreased with increases in distending pressures. We conclude that oxyhemoglobin has a direct inhibitory effect on lymphatic smooth muscle. The ability of oxyhemoglobin to alter the pressure range over which the lymph pump operates appears to be dependent on an intact endothelium.

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Key role of l-alanine in the control of hepatic protein synthesis

Biochemical Journal ◽

10.1042/bj2410491 ◽

1987 ◽

Vol 241 (2) ◽

pp. 491-498 ◽

Cited By ~ 26

Author(s):

D Pérez-Sala ◽

R Parrilla ◽

M S Ayuso

Keyword(s):

Amino Acids ◽

Protein Synthesis ◽

Physiological Role ◽

Chain Elongation ◽

Liver Protein ◽

Isolated Liver Cells ◽

Metabolic Transformation ◽

Hepatic Protein Synthesis

We investigated the effects of administration of single amino acids to starved rats on the regulation of protein synthesis in the liver. Of all the amino acids tested, only alanine, ornithine and proline promoted statistically significant increases in the extent of hepatic polyribosome aggregation. The most effective of these was alanine, whose effect of promoting polyribosomal aggregation was accompanied by a decrease in the polypeptide-chain elongation time. The following observations indicate that alanine plays an important physiological role in the regulation of hepatic protein synthesis. Alanine was the amino acid showing the largest decrease in hepatic content in the transition from high (fed) to low (starved) rates of protein synthesis. The administration of glucose or pyruvate is also effective in increasing liver protein synthesis in starved rats, and their effects were accompanied by an increased hepatic alanine content. An increase in hepatic ornithine content does not lead to an increased protein synthesis, unless it is accompanied by an increase of alanine. The effect of alanine is observed either in vivo, in rats pretreated with cycloserine to prevent its transamination, or in isolated liver cells under conditions in which its metabolic transformation is fully impeded.

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Role of enkephalins in regulation of basal intestinal water and ion absorption in the rat

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1984.246.4.g386 ◽

1984 ◽

Vol 246 (4) ◽

pp. G386-G392

Author(s):

R. Fogel ◽

R. B. Kaplan

Keyword(s):

Receptor Antagonist ◽

Water Transport ◽

Opiate Receptor ◽

Ion Absorption ◽

Mu Receptors ◽

Induced Changes ◽

Delta Receptor ◽

Mu Opiate Receptor

Intraluminal administration of naloxone (10(-4) M), a mu-opiate receptor antagonist, or diprenorphine (10(-6) M), an opiate receptor antagonist with high affinity for both delta- and mu-receptors, decreased basal in vivo water and electrolyte absorption in the jejunum and ileum but not the colon of the rat. Diprenorphine (10(-5) M) decreased basal colonic water transport. These changes were not due to a reduction in mucosal Na-K-ATPase activity. Intravenous atropine prevented as well as abolished the changes in water transport due to naloxone. The diprenorphine-induced changes were not altered by atropine. Naloxone and diprenorphine acted by different receptors. Pretreatment with naloxone (10(-4) M) prevented the increase in water transport due to morphine, a mu-agonist, whereas a higher concentration of naloxone (10(-3) M) was required to inhibit the increase due to D-Ala-methionine-enkephalinamide, a delta-receptor agonist. In contrast, diprenorphine (10(-6) M) abolished the absorption caused by morphine and D-Ala-methionine-enkephalinamide. Diprenorphine (3 X 10(-7) M) partially prevented the morphine-induced increase in water absorption.(ABSTRACT TRUNCATED AT 250 WORDS)

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Citrulline directly modulates muscle protein synthesis via the PI3K/MAPK/4E-BP1 pathway in a malnourished state: evidence from in vivo, ex vivo, and in vitro studies

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00203.2016 ◽

2017 ◽

Vol 312 (1) ◽

pp. E27-E36 ◽

Cited By ~ 16

Author(s):

Servane Le Plénier ◽

Arthur Goron ◽

Athanassia Sotiropoulos ◽

Eliane Archambault ◽

Chantal Guihenneuc ◽

...

Keyword(s):

Protein Synthesis ◽

Ex Vivo ◽

Muscle Protein ◽

Muscle Protein Synthesis ◽

Fold Increase ◽

Underlying Mechanism ◽

Muscle Homeostasis

Citrulline (CIT) is an endogenous amino acid produced by the intestine. Recent literature has consistently shown CIT to be an activator of muscle protein synthesis (MPS). However, the underlying mechanism is still unknown. Our working hypothesis was that CIT might regulate muscle homeostasis directly through the mTORC1/PI3K/MAPK pathways. Because CIT undergoes both interorgan and intraorgan trafficking and metabolism, we combined three approaches: in vivo, ex vivo, and in vitro. Using a model of malnourished aged rats, CIT supplementation activated the phosphorylation of S6K1 and 4E-BP1 in muscle. Interestingly, the increase in S6K1 phosphorylation was positively correlated ( P < 0.05) with plasma CIT concentration. In a model of isolated incubated skeletal muscle from malnourished rats, CIT enhanced MPS (from 30 to 80% CIT vs. Ctrl, P < 0.05), and the CIT effect was abolished in the presence of wortmannin, rapamycin, and PD-98059. In vitro, on myotubes in culture, CIT led to a 2.5-fold increase in S6K1 phosphorylation and a 1.5-fold increase in 4E-BP1 phosphorylation. Both rapamycin and PD-98059 inhibited the CIT effect on S6K1, whereas only LY-294002 inhibited the CIT effect on both S6K1 and 4E-BP1. These findings show that CIT is a signaling agent for muscle homeostasis, suggesting a new role of the intestine in muscle mass control.

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The effects of 6 hours of hypoxia on protein synthesis in rat tissues in vivo and in vitro

Biochemical Journal ◽

10.1042/bj2280179 ◽

1985 ◽

Vol 228 (1) ◽

pp. 179-185 ◽

Cited By ~ 58

Author(s):

V R Preedy ◽

D M Smith ◽

P H Sugden

Keyword(s):

Protein Synthesis ◽

Gastric Emptying ◽

Skeletal Muscles ◽

Rat Tissues ◽

Tissue Nitrogen ◽

The Brain ◽

H Protein

Rates of protein synthesis were measured in vivo in several tissues (heart, skeletal muscles, liver, tibia, skin, brain, kidney, lung) of fed rats exposed to O2/N2 (1:9) for 6 h starting at 08:00-11:00 h. Protein synthesis rates were depressed by 15-35% compared with normoxic controls in all of the tissues studied. The decreases were greatest in the brain and the skin. Although hypoxia inhibited gastric emptying, its effects on protein synthesis could probably not be attributed to its induction of a starved state, because protein-synthesis rates in brain and skin were not decreased by a 15-18 h period of starvation initiated at 23:00 h. Furthermore, we showed that protein synthesis was inhibited by hypoxia in the rat heart perfused in vitro, suggesting a direct effect. The role of hypoxia in perturbing tissue nitrogen balance in various physiological and pathological states is discussed.

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Differential role of glucocorticoids in mediating endotoxin-induced changes in IGF-I and IGFBP-1

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1997.272.6.r1990 ◽

1997 ◽

Vol 272 (6) ◽

pp. R1990-R1997 ◽

Cited By ~ 17

Author(s):

Y. H. Li ◽

J. Fan ◽

C. H. Lang

Keyword(s):

Plasma Corticosterone ◽

Mrna Abundance ◽

Male Rats ◽

Ru 486 ◽

Igf I ◽

Igf Binding ◽

Induced Changes ◽

Igf Binding Protein

The purpose of the present study was to determine whether endogenous elevations in glucocorticoids mediate the changes in insulin-like growth factor (IGF) 1 and IGF binding protein (IGFBP) 1 levels in plasma and tissues observed after in vivo administration of lipopolysaccharide (LPS). In overnight-fasted male rats LPS injected via the tail vein decreased the IGF-I concentration in plasma, liver, and skeletal muscle (30-45%) and increased IGF-I content in kidney (approximately 3-fold). LPS also decreased IGF-I mRNA abundance in liver and muscle and increased gene expression in kidney. Concomitantly, IGFBP-1 levels in plasma, liver, and muscle were markedly elevated by LPS. All these changes were associated with a greater than fourfold elevation in plasma corticosterone. Pretreatment of rats with the glucocorticoid receptor antagonist RU-486 completely prevented or blunted the LPS-induced changes in IGF-I content in plasma, liver, muscle, and kidney. In liver and muscle RU-486 significantly attenuated the reduction in IGF-I mRNA abundance produced by LPS, but in kidney the LPS-induced increase in IGF-I mRNA was still evident. In contrast, pretreatment with RU-486 did not prevent or attenuate the LPS-induced increase in IGFBP-1 levels in plasma, liver, or muscle. These data suggest that glucocorticoids play a major role in regulating IGF-I mRNA and peptide content in tissues in response to LPS, but the increased IGFBP-1 in blood and tissues induced by LPS appears largely glucocorticoid independent.

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