scholarly journals Insulin-stimulated α-(methyl)aminoisobutyric acid uptake in skeletal muscle. Evidence for a short-term activation of uptake independent of Na+ electrochemical gradient and protein synthesis

1988 ◽  
Vol 253 (3) ◽  
pp. 625-629 ◽  
Author(s):  
A Gumà ◽  
X Testar ◽  
M Palacín ◽  
A Zorzano
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Insulin Action ◽  
De Novo ◽  
Acid Transport ◽  
Electrochemical Gradient ◽  
Aminoisobutyric Acid ◽  
System A ◽  
Stimulation Of

1. The present study was designed to explore the mechanisms by which insulin stimulates system A of amino acid transport in extensor digitorum longus (EDL) muscles, by using a system A analogue, alpha-(methyl)aminoisobutyric acid (MeAIB). 2. Insulin stimulation of MeAIB uptake was noted after only 30 min of incubation and was maximal at 60 min. Kinetics of the insulin effect on MeAIB uptake were characterized by an increased Vmax. without modification of Km for MeAIB. 3. Incubation of EDL muscles with cycloheximide for 90 min did not modify MeAIB uptake in either the presence or the absence of insulin, indicating the independence of insulin action from protein synthesis de novo. Incubations for 180 min with cycloheximide caused a decrease in basal MeAIB uptake; however, the percentage stimulation of amino acid transport by insulin was unaltered. Basal MeAIB uptake was increased by incubation for 180 min, but under these conditions no change in the percentage effect of insulin was found. 4. Ouabain, gramicidin D, or both, markedly decreased basal MeAIB uptake by EDL muscle, but the percentage effect of insulin was unaltered. 5. We conclude that insulin action on amino acid transport through system A in muscle is rapid, is characterized by an increased Vmax., and is independent of protein synthesis de novo and the Na+ electrochemical gradient. Our data are compatible with insulin acting directly on the system A transporter.

Stimulation of transport of alpha-aminoisobutyric acid into the testes of immature mice in vivo by follicle-stimulating hormone

1982 ◽  
Vol 100 (1) ◽  
pp. 137-142
Author(s):  
Nila Oza ◽  
Sarah J. Meanock ◽  
A. G. Davies
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Specific Activity ◽  
Follicle Stimulating Hormone ◽  
Acid Transport ◽  
Aminoisobutyric Acid ◽  
Old Mice ◽  
Stimulation Of

Abstract. Groups of immature mice were injected sc with radiocarbon-labelled alpha-aminoisobutyric acid (AIB) after being given a single sc injection of hFSH or of 0.9% saline. As an index of the transport of AIB, the specific activity of isotope was measured in homogenates of testis and of liver. FSH treatment caused statistically significant increases in the specific activity of isotope in the testes and in the ratio of testicular to liver specific activity. The effect was greatest in 9-day-old mice injected with FSH 16 h before removal of the testes. Uptake of labelled AIB was not stimulated after administration of hCG or testosterone. Doses of cycloheximide sufficient to reduce the rate of protein synthesis by over 99% did not impair testicular uptake of labelled AIB or the influence of FSH on AIB uptake. These results suggest that FSH stimulates amino acid transport into cells of the immature testis and that this action is independent of the stimulatory effect of FSH on testicular protein synthesis.

Ceramide down‐regulates System A amino acid transport and protein synthesis in rat skeletal muscle cells

2004 ◽  
Vol 19 (3) ◽  
pp. 1-24 ◽  
Author(s):  
Russell Hyde ◽  
Eric Hajduch ◽  
Darren J. Powell ◽  
Peter M. Taylor ◽  
Harinder S. Hundal
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Acid Transport ◽  
Rat Skeletal Muscle ◽  
System A

The stimulation of Na,K,Cl cotransport and of system A for neutral amino acid transport is a mechanism for cell volume increase during the cell cycle

1996 ◽  
Vol 10 (8) ◽  
pp. 920-926 ◽  
Author(s):  
Ovidio Bussolati ◽  
Jacopo Uggeri ◽  
Silvana Belletti ◽  
Valeria Dall'Asta ◽  
Gian C. Gazzola
Keyword(s):  
Cell Cycle ◽  
Amino Acid ◽  
Cell Volume ◽  
Amino Acid Transport ◽  
Neutral Amino Acid ◽  
Acid Transport ◽  
Volume Increase ◽  
System A ◽  
Stimulation Of

System A amino acid transport in incubated muscle: effects of insulin and acute uremia

1986 ◽  
Vol 251 (1) ◽  
pp. F74-F80
Author(s):  
B. J. Maroni ◽  
G. Karapanos ◽  
W. E. Mitch
Keyword(s):  
Amino Acid ◽  
Amino Acid Transport ◽  
Insulin Dose ◽  
Amino Acid Uptake ◽  
Similar Degree ◽  
Acid Uptake ◽  
Acid Transport ◽  
Insulin Resistant ◽  
System A ◽  
Stimulation Of

The insulin-stimulated increase in amino acid uptake in most cells and tissues involves stimulation of system A transport. In muscle the probes used to study this process have not been specific, making it difficult to determine whether system A is abnormal in insulin-resistant states, such as acute renal failure (ARF). To circumvent this problem, we studied 2-(methylamino) isobutyrate (MeAIB) transport. Its specificity for system A in incubated rat epitrochlearis muscles was documented by showing its uptake by only one carrier that is sodium dependent and insulin responsive and that exhibits adaptive regulation in response to starvation. Using this specific probe we determined whether insulin-stimulated amino acid transport by system A is impaired by ARF. MeAIB uptake was linear for 3 h in muscles of ARF and sham-operated (SO) rats. In the absence (basal) or presence of insulin, MeAIB uptake was significantly lower in ARF, yet the stimulation by insulin was similar in both groups. Likewise, the insulin dose-response relationship confirmed that physiological levels of insulin (less than or equal to 10(2) microU/ml) increased transport by a similar degree. At greater than or equal to 10(2) microU/ml insulin there was a plateau in MeAIB transport in ARF but not in SO muscles. Thus basal system A transport is depressed in ARF, but the stimulation of system A by physiological levels of insulin is preserved. At pharmacological levels of insulin system A transport is impaired by ARF.

scholarly journals Modulation by betaine of cellular responses to osmotic stress

1992 ◽  
Vol 282 (1) ◽  
pp. 69-73 ◽  
Author(s):  
P G Petronini ◽  
E M De Angelis ◽  
P Borghetti ◽  
A F Borghetti ◽  
K P Wheeler
Keyword(s):  
Cell Proliferation ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Cell Protein ◽  
Acid Transport ◽  
3T3 Cells ◽  
Functional Responses ◽  
Cell Functions ◽  
System A

Various solutes were tested to see if they could modify the responses of SV-3T3 cells to hyperosmotic (0.5 osM) conditions, which cause an inhibition of general cell protein synthesis and of the rate of cell proliferation, coupled with an induction of amino acid transport activity. The added solutes were glycerol, proline, taurine, betaine, dimethylglycine and sarcosine. Of these, betaine produced the most dramatic and consistent effects. Addition of 10-25 mM-betaine to the hyperosmotic medium largely prevented the 90% inhibition of cell proliferation that occurred in its absence. Whether it was added initially or after the cells were exposed to hyperosmotic medium, 25 mM-betaine also converted a 50% recovery of the rate of protein synthesis into 100%. Similarly, the same concentrations of betaine prevented a 30% decrease in cell volume and decreased the induction of amino acid transport via system A by 73%. Lower concentrations of betaine produced smaller but still significant changes in these functional responses. With chick-embryo fibroblasts, under identical hyperosmotic conditions, 25 mM-betaine completely counteracted a 75% inhibition of the rate of protein synthesis. At present it is not clear how betaine modulates these effects of hyperosmolarity on cell functions.

Amino Acid Transport into Human Platelets and Subsequent Incorporation into Protein

1970 ◽  
Vol 23 (01) ◽  
pp. 140-147 ◽  
Author(s):  
I. A Cooper ◽  
B. G Firkin
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
De Novo ◽  
Human Platelets ◽  
Acid Transport ◽  
Protein Components ◽  
De Novo Protein Synthesis ◽  
Subsequent Incorporation

SummaryHuman platelets are known to contain various protein components. Among them are fibrinogen and other soluble proteins. The origin of such proteins has not been clear.Studies were designed to demonstrate the ability of the platelet to incorporate amino acids and subsequently utilise these for de novo protein synthesis.Seven different 14C labelled amino acids were used, cysteine, lysine, serine, glutamic acid, proline, valine und leucine.Active incorporation into platelets of all these amino acids was demonstrated with some evidence for incorporation of cysteine, lysine and serine into the fibrinogen and soluble protein.

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