The effect of insulin <i>in vitro</i> on the accumulation of amino acids by isolated rat diaphragm

Manchester, K.L.; Young, F. G.

doi:10.1042/bj0750487

Cited by 101 publications

(44 citation statements)

References 17 publications

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“…Insulin, which has been reported to accelerate the uptake ofamino acids by rat diaphragm (Manchester & Young, 1960), had no effect on the removal of glutamate from the perfusion medium or on the synthesis of glucose when-added as a single dose of 0'075unit/ml. at 40min.…”

Section: Methodsmentioning

confidence: 96%

The rate of gluconeogenesis from various precursors in the perfused rat liver

Ross

Hems

Krebs

1967

Biochemical Journal

392

139

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1. The rates of gluconeogenesis from many precursors have been measured in the perfused rat liver and, for comparison, in rat liver slices. All livers were from rats starved for 48hr. Under optimum conditions the rates in perfused liver were three to five times those found under optimum conditions in slices. 2. Rapid gluconeogenesis (rates of above 0-5,.umole/g./min.) were found with lactate, pyruvate, alanine, serine, proline, fructose, dihydroxyacetone, sorbitol, xylitol. Unexpectedly other amino acids, notably glutamate and aspartate, and the intermediates of the tricarboxylic acid cycle (with the exception of oxaloacetate), reacted very slowly and were not readily removed from the perfusion medium, presumably because of permeability barriers which prevent the passage of highly charged negative ions. Glutamine and asparagine formed glucose more readily than the corresponding amino acids. 3. Glucagon increased the rate of gluconeogenesis from lactate and pyruvate but not from any other precursor tested. This occurred when the liver was virtually completely depleted ofglycogen. Two sites of action of glucagon must therefore be postulated: one concerned with mobilization of liver glycogen, the other with the promotion of gluconeogenesis. Sliced liver did not respond to glucagon. 4. Pyruvate and oxaloacetate formed substantial quantities of lactate on perfusion, which indicates that the reducing power provided in the cytoplasm was in excess of the needs of gluconeogenesis. 5. Values for the content of intermediary metabolites of gluconeogenesis in the perfused liver are reported. The values for most intermediates rose on addition of lactate. 6. The rates of gluconeogenesis from lactate and pyruvate were not affected by wide variations of the lactate/pyruvate ratio in the perfusion medium.

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Section: Methodsmentioning

confidence: 96%

The rate of gluconeogenesis from various precursors in the perfused rat liver

Ross

Hems

Krebs

1967

Biochemical Journal

392

139

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“…The passage of amino acids into cells by means of carriermediated transport mechanisms is well established in other tissues (Neame, 1968). In the case of muscle, some in vitro work has shown that for a few amino acids entry is by carrier-mediated transport (Manchester & Young, 1960;Akedo & Christensen, 1962;Bombara & Bergamini, 1968). (%) [14C]L-Phenylalanine The present work shows that for some amino acids carrier transport is operating in the living animal, for there is firm evidence that L-lysine and L-threonine enter muscle by an active mechanism.…”

Section: Discussionmentioning

confidence: 99%

The movement of amino acids between blood and skeletal muscle in the rat

Baños¹,

Daniel²,

Moorhouse³

et al. 1973

The Journal of Physiology

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SUMMARY1. The rates of entry of twenty of the blood amino acids into skeletal muscle of living rats were measured directly by means of a technique which ensured that a steady concentration of a radioactively labelled amino acid is reached rapidly and is maintained in the bloodstream.2. The rates of entry were measured in experiments of short duration to avoid possible artifacts caused by amino acids leaving the muscle or by their metabolism.3. The entry rate of each amino acid increased in direct proportion to its concentration in the blood plasma over the physiological range.4. The various amino acids had widely different rates of entry. These rates could not be correlated with the physicochemical properties of the amino acids.5. Two amino acids, L-lysine and L-threonine, enter muscle against a concentration gradient, while in the case of a third, L-arginine, the blood concentration was raised high enough to induce saturation of the entry mechanism.6. It is concluded that entry takes place in vivo by means of carriermediated transport processes with a high degree of specificity.7. When the concentration of an amino acid in the bloodstream was increased to about twice normal the proportion of the additional amino acid that was taken up rapidly by the muscle was large enough, especially for the essential amino acids, to suggest that the tissue constitutes a quantitatively important storage system helping to regulate the concentrations of amino acids in the bloodstream.

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“…Since results with these two methods were in very good agreement, the boiling water technique was used for all future work. When incorporation of amino acids into tissue protein was being studied as well as amino acid uptake, the cell debris was taken up in 5% trichloroacetic acid, and the isotopically labeled tissue protein prepared and counted according to previously described techniques (13,14).…”

Section: Methodsmentioning

confidence: 99%