De novo synthesis of alanine by the perfused rat hindlimb

1976 ◽  
Vol 230 (5) ◽  
pp. 1379-1384 ◽  
Author(s):  
B Grubb
Keyword(s):  
Glucose Uptake ◽  
Glucose Concentration ◽  
De Novo ◽  
Glucose Measurement ◽  
De Novo Synthesis ◽  
Bicarbonate Buffer ◽  
Large Production ◽  
Alanine Synthesis ◽  
Alanine Production ◽  
Isolated Rat

Due to the disproportionately large production of alanine by muscle, it has been suggested that part of the alanine released by muscle is synthesized de novo by the transamination of glucose-derived pyruvate. This glucose-alanine conversion was quantitated in the isolated rat hindlimb perfused with a solution of bicarbonate buffer containing 2% albumin, 2.4% dextran, 2.5-15.9 mM glucose, 32-34% dog erythrocytes, and 0.05 muCi/ml [14C]glucose. Measurement of labeled alanine production allowed quantitation of de novo alanine synthesis. De novo derived alanine accounted for an average of 33% of the total alanine released by the perfused tissue (perfusate glucose concentration 8.3 mM), concurrently 2.7% of the glucose taken up by the limb was converted to alanine. By increasing the glucose concentration perfusing the muscle, both the rate of glucose uptake and de novo alanine release were increased. Addition of insulin to the perfusate (700 muU/ml) resulted in a significant increase in the rate of glucose uptake and de novo alanine production, but the rate of total alanine release was significantly decreased by the hormone. It was concluded that de novo alanine production accounts for a sizeable portion of the total alanine released by muscle, nevertheless a comparatively small fraction of the glucose carbons are actually transformed to alanine.

Determinants of kinin release in isolated rat hindquarters

1998 ◽  
Vol 274 (1) ◽  
pp. R120-R125 ◽  
Author(s):  
Tohru Sakakibara ◽  
Thomas H. Hintze ◽  
Alberto Nasjletti
Keyword(s):  
Protein Synthesis ◽  
Trypsin Inhibitor ◽  
De Novo ◽  
Soybean Trypsin Inhibitor ◽  
Protein Synthesis Inhibitor ◽  
Synthesis Inhibitor ◽  
Bicarbonate Buffer ◽  
Kallikrein Inhibitor ◽  
Isolated Rat

We studied the determinants of kinin release into the venous effluent of rat hindquarters perfused with Krebs bicarbonate buffer. Kinin release in preparations perfused with control media (14.6 ± 2.5–20.7 ± 6.7 pg/15 min) was surpassed by that in preparations perfused with media containing kininase inhibitors (243 ± 53 to 276 ± 78 pg/15 min). Kinin release increased when purified kininogen (from 242 ± 43 to 3,365 ± 725 pg/15 min) or kallikrein (from 270 ± 49 to 30,649 ± 8,040 pg/15 min) was added to the perfusate. Conversely, kinin release fell when the kallikrein inhibitor aprotinin (from 272 ± 58 to 122 ± 27 pg/15 min) or soybean trypsin inhibitor (from 273 ± 52 to 195 ± 25 pg/15 min) was added. Both basal and kininogen-induced kinin release were attenuated in preparations perfused with media containing cycloheximide, a protein synthesis inhibitor, but kallikrein-induced kinin release was not. These data suggest that kinin release from perfused rat hindquarters reflects the activity of both the kinin-degrading and kinin-generating pathways and that the latter is sustained by a kallikrein manufactured de novo and by preexistent kininogen(s).

scholarly journals Glucose uptake in brown fat cells is dependent on mTOR complex 2–promoted GLUT1 translocation

2014 ◽  
Vol 207 (3) ◽  
pp. 365-374 ◽  
Author(s):  
Jessica M. Olsen ◽  
Masaaki Sato ◽  
Olof S. Dallner ◽  
Anna L. Sandström ◽  
Didier F. Pisani ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Glucose Uptake ◽  
De Novo ◽  
De Novo Synthesis ◽  
Mechanistic Target Of Rapamycin ◽  
Brown Adipose ◽  
Phosphoinositide 3 Kinase ◽  
Very High ◽  
Different Parts

Brown adipose tissue is the primary site for thermogenesis and can consume, in addition to free fatty acids, a very high amount of glucose from the blood, which can both acutely and chronically affect glucose homeostasis. Here, we show that mechanistic target of rapamycin (mTOR) complex 2 has a novel role in β3-adrenoceptor–stimulated glucose uptake in brown adipose tissue. We show that β3-adrenoceptors stimulate glucose uptake in brown adipose tissue via a signaling pathway that is comprised of two different parts: one part dependent on cAMP-mediated increases in GLUT1 transcription and de novo synthesis of GLUT1 and another part dependent on mTOR complex 2–stimulated translocation of newly synthesized GLUT1 to the plasma membrane, leading to increased glucose uptake. Both parts are essential for β3-adrenoceptor–stimulated glucose uptake. Importantly, the effect of β3-adrenoceptor on mTOR complex 2 is independent of the classical insulin–phosphoinositide 3-kinase–Akt pathway, highlighting a novel mechanism of mTOR complex 2 activation.

Effects of carbohydrates on secretion of insulin from isolated rat pancreas

1963 ◽  
Vol 205 (4) ◽  
pp. 638-644 ◽  
Author(s):  
Gerold M. Grodsky ◽  
Adrienne A. Batts ◽  
Leslie L. Bennett ◽  
Carl Vcella ◽  
Nancy B. McWilliams ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Glucose Concentration ◽  
Islet Cell ◽  
De Novo ◽  
Experimental Period ◽  
Rat Pancreas ◽  
Stimulate Insulin Secretion ◽  
Isolated Rat

The effect of carbohydrates on the secretion of immunochemically measurable insulin was studied in an isolated perfused pancreatic preparation from the rat. Degradation of circulating insulin (as measured by chromatographic examination of added insulin-I131) was less than 15% during the 4-hr experimental period. Without the addition of glucose, or at glucose concentrations of less than 50 mg/100 ml, insulin secretion was not detectable. At glucose concentrations of 50–150 mg/100 ml, insulin secretion occurred immediately and persisted throughout the experimental period. Insulin secretion was further increased by increasing glucose concentration to 150–500 mg/100 ml. The incidence of islet cell degranulation increased with increasing insulin secretion, suggesting that glucose stimulated secretion of stored insulin faster than synthesis of insulin de novo. Galactose, xylose, l-arabinose, pyruvate, and 2-deoxyglucose in concentrations of 600 mg/100 ml did not stimulate insulin secretion. Mannose stimulated the pancreas equally as well as glucose. Fructose was also active, but was less effective than glucose. Neither 2-deoxyglucose nor galactose blocked the insulin secretion by glucose. The data suggest that secretion of insulin is stimulated by a metabolite or a product resulting from the metabolism of glucose which can also be supplied by other metabolizable sugars.

scholarly journals 103 Equine enterocytes actively oxidize L-glutamine but do not synthesize L-citrulline and L-arginine from L-glutamine or L-proline in vitro

2020 ◽  
Vol 98 (Supplement_4) ◽  
pp. 90-91
Author(s):  
Rafael E Martinez ◽  
Jessica L Leatherwood ◽  
Amanda N Bradbery ◽  
Mattea L Much ◽  
Brittany L Silvers ◽  
...  
Keyword(s):  
Liquid Scintillation ◽  
De Novo ◽  
Scintillation Counter ◽  
Initial Step ◽  
Positive Control ◽  
Co2 Production ◽  
De Novo Synthesis ◽  
Bicarbonate Buffer ◽  
Dietary Requirements

Abstract In many mammals, enterocytes are responsible for the synthesis of L-citrulline and L-arginine from L-glutamine and L-proline. However, there is limited research in the horse to determine de novo synthesis of L-citrulline or L-arginine by the enterocyte, which is the initial step in establishing dietary requirements and comprehending arginine nutrition in horses. We utilized jejunal enterocytes from 20 horses (neonate n = 2, mature n = 16, and geriatric n = 2) to study glutamine and proline metabolism. As a positive control, enterocytes were isolated from 0, 60, and 180-day old pigs (n = 8/age group). Equine or porcine enterocytes were incubated at 37oC for 30 min in oxygenated (95% O2/5% CO2) Krebs bicarbonate buffer (pH 7.4) containing 5 mM D-glucose and either 2 mM L-[U-14C]glutamine or 2 mM L-[U-14C]proline plus 2 mM L-glutamine. Collected 14CO2 was determined by a liquid scintillation counter, whereas amino acids in cells plus medium were analyzed by HPLC. Both equine and porcine enterocytes oxidized glutamine to CO2 but had a limited ability to oxidize proline to CO2, confirming the biochemical viability of the cells in vitro. Enterocytes from neonatal and geriatric horses had lower rates (nmol/106 cells/30 min) of CO2 production (1.10 ± 0.52 and 1.31 ± 0.65, respectively) from glutamine than those (40.9 ± 5.40) from mature horses. Porcine enterocytes synthesized L-citrulline and L-arginine from glutamine and proline (e.g., 4.86 ± 0.26 nmol L-citrulline/mg protein/30 min and 0.85 ± 0.04 nmol L-arginine/mg protein/30 min from glutamine in enterocytes of 60-day-old pigs). In contrast, equine enterocytes did not synthesize L-citrulline and L-arginine from L-glutamine or L-proline. Because L-arginine is an essential substrate for the synthesis of protein, nitric oxide, and creatine, our novel findings on the lack of intestinal synthesis of L-arginine in horses have important implications for their nutrition, metabolism, and health.

Characterization of Monocyte-Associated Factor V

1993 ◽  
Vol 70 (02) ◽  
pp. 273-280 ◽  
Author(s):  
Janos Kappelmayer ◽  
Satya P Kunapuli ◽  
Edward G Wyshock ◽  
Robert W Colman
Keyword(s):  
Monoclonal Antibody ◽  
Light Chain ◽  
Peripheral Blood ◽  
De Novo ◽  
Factor V ◽  
Blood Monocytes ◽  
De Novo Synthesis ◽  
Hep G2 ◽  
Hep G2 Cells ◽  
Peripheral Blood Monocytes

SummaryWe demonstrate that in addition to possessing binding sites for intact factor V (FV), unstimulated peripheral blood monocytes also express activated factor V (FVa) on their surfaces. FVa was identified on the monocyte surface by monoclonal antibody B38 recognizing FVa light chain and by human oligoclonal antibodies H1 (to FVa light chain) and H2 (to FVa heavy chain) using immunofluorescence microscopy and flow cytometry. On Western blots, partially cleaved FV could be identified as a 220 kDa band in lysates of monocytes. In addition to surface expression of FVa, monocytes also contain intracellular FV as detected only after permeabilization by Triton X-100 by monoclonal antibody B10 directed specifically to the Cl domain not present in FVa. We sought to determine whether the presence of FV in peripheral blood monocytes is a result of de novo synthesis.Using in situ hybridization, no FV mRNA could be detected in monocytes, while in parallel control studies, factor V mRNA was detectable in Hep G2 cells and CD18 mRNA in monocytes. In addition, using reverse transcriptase and the polymerase chain reaction, no FV mRNA was detected in mononuclear cells or in U937 cells, but mRNA for factor V was present in Hep G2 cells using the same techniques. These data suggest that FV is present in human monocytes, presumably acquired by binding of plasma FV, and that the presence of this critical coagulation factor is not due to de novo synthesis.

Platelets Stimulate Thromboplastin Synthesis in Human Endothelial Cells

1983 ◽  
Vol 49 (02) ◽  
pp. 069-072 ◽  
Author(s):  
U L H Johnsen ◽  
T Lyberg ◽  
K S Galdal ◽  
H Prydz
Keyword(s):  
Endothelial Cells ◽  
De Novo ◽  
Umbilical Vein ◽  
Time Dependent ◽  
De Novo Synthesis ◽  
Human Endothelial Cells ◽  
Tumor Promotor ◽  
Coagulation Assay ◽  
Platelet Aggregates ◽  
Umbilical Vein Endothelial Cells

SummaryHuman umbilical vein endothelial cells in culture synthesize thromboplastin upon stimulation with phytohaemagglutinin (PHA) or the tumor promotor 12-O-tetradecanoyl-phorbol-13-acetate (TPA). The thromboplastin activity is further strongly enhanced in a time dependent reaction by the presence of gel-filtered platelets or platelet aggregates. This effect was demonstrable at platelet concentrations lower than those normally found in plasma, it may thus be of pathophysiological relevance. The thromboplastin activity increased with increasing number of platelets added. Cycloheximide inhibited the increase, suggesting that de novo synthesis of the protein component of thromboplastin, apoprotein III, is necessary.When care was taken to remove monocytes no thromboplastin activity and no apoprotein HI antigen could be demonstrated in suspensions of gel-filtered platelets, platelets aggregated with thrombin or homogenized platelets when studied with a coagulation assay and an antibody neutralization technique.

DE NOVO SYNTHESIS OF STEROIDS BY THE TESTES OF THE HUMAN FOETUS AT MIDGESTATION

1971 ◽  
Vol 68 (1_Supplb) ◽  
pp. S135 ◽  
Author(s):  
R. S. Mathur ◽  
N. Wiqvist ◽  
E. Diczfalusy
Keyword(s):  
De Novo ◽  
De Novo Synthesis ◽  
Human Foetus
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