scholarly journals NET BLOOD EXCHANGE OF BRANCHED-CHAIN AMINO AND α-KETO ACIDS ACROSS THE PORTAL-DRAINED VISCERA AND HINDLIMB OF CATTLE DURING INFUSIONS OF LEUCINE AND INSULIN

1989 ◽  
Vol 69 (1) ◽  
pp. 131-140 ◽  
Author(s):  
R. J. EARLY ◽  
J. R. THOMPSON ◽  
R. J. CHRISTOPHERSON
Keyword(s):  
Amino Acid ◽  
Key Words ◽  
Plasma Glucose ◽  
Whole Blood ◽  
Fold Increase ◽  
Keto Acid ◽  
Branched Chain Amino Acid ◽  
Keto Acids ◽  
Blood Exchange ◽  
Branched Chain

The effects of intra external iliac arterial infusions of leucine (114 μmol h−1 kg0.75) and insulin (0.34 U h−1 kg0.75) into the hindlimb on net whole blood branched-chain amino acid (BCAA), plasma branched-chain α-keto acid (BCKA) and glucose exchange across the hindlimb (HL) and portal-drained viscera (PDV) were investigated in chronically catheterized cattle. Leucine infusions increased (P < 0.05) arterial leucine and α-ketoisocaproate concentrations but did not affect the concentrations of other BCAA, BCKA or glucose. Leucine infusions resulted in a 4-fold increase (P < 0.1) in the net HL removal of leucine and a small increase (P < 0.1) in the net HL release of α-ketoisocaproate. Net whole blood BCAA, plasma BCKA and plasma glucose exchange across the PDV were unaffected by leucine infusions. Insulin infusions decreased (P < 0.1) whole blood leucine, plasma α-ketoisocaproate and plasma glucose concentrations and increased (P < 0.1) the HL extraction of plasma glucose. The HL and PDV extraction of whole blood BCAA and plasma BCKA were unaffected by insulin infusions. The data suggest that cattle are less sensitive to the effects of leucine and insulin on tissue BCAA catabolism compared to nonruminant species. Key words: Branched-chain amino acid, branched-chain α-keto acid, leucine, insulin, cattle

BLOOD BRANCHED-CHAIN AMINO AND α-KETO ACID CONCENTRATIONS AND NET EXCHANGE ACROSS THE PORTAL-DRAINED VISCERA AND HINDLIMB OF FED AND FASTED RUMINANTS

1987 ◽  
Vol 67 (4) ◽  
pp. 1011-1020 ◽  
Author(s):  
RICHARD J. EARLY ◽  
JAMES R. THOMPSON ◽  
ROBERT J. CHRISTOPHERSON ◽  
GARY W. SEDGWICK
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Hind Limb ◽  
Venous Blood ◽  
Branched Chain Amino Acids ◽  
Keto Acid ◽  
Branched Chain Amino Acid ◽  
Keto Acids ◽  
Branched Chain ◽  
Cattle And Sheep

In the first of two experiments, whole blood branched-chain amino acid (BCAA) and plasma branched-chain α-keto acid (BCKA) concentrations in jugular venous blood were determined in cattle and sheep before and during a 6-d fast. In cattle, concentrations of valine, isoleucine, α-ketoisovalerate (KIV) and α-ketomethylvalerate (KMV) remained unchanged whereas leucine and α-ketoisocaproate (KTC) increased (P < 0.05) during fasting. In sheep, only KIV and KMV remained unchanged whereas BCAA and KIC increased (P < 0.05) during fasting. In a second experiment on cattle chronically catheterized to measure BCAA and BCKA exchange across the portal-drained viscera (PDV) and hindlimb (HL), the PDV added and the HL removed BCAA from the blood of fed cattle. The opposite exchange occurred after a 6-d fast. Releases of BCKA from the PDV and HL in both fed and fasted states were small compared to BCAA exchanges. The data suggest that blood BCAA but not BCKA concentrations may respond differently to starvation in sheep versus cattle and that in cattle the PDV and HL do not release appreciable amounts of BCKA relative to the net movements of the BCAA. Key words: Portal-drained viscera, hind limb, branched-chain amino acids, branched-chain α-keto acids, fasting, ruminants

Regulation of valine and alpha-ketoisocaproate metabolism in rat kidney mitochondria

1988 ◽  
Vol 255 (4) ◽  
pp. E475-E481 ◽  
Author(s):  
R. H. Miller ◽  
A. E. Harper
Keyword(s):  
Amino Acid ◽  
Rat Kidney ◽  
Co2 Evolution ◽  
Radioactive Tracers ◽  
Keto Acid ◽  
Kidney Mitochondria ◽  
Assay Medium ◽  
Branched Chain Amino Acid ◽  
Keto Acids ◽  
Branched Chain

Activities of branched-chain amino acid (BCAA) aminotransferase (BCAT) and alpha-keto acid dehydrogenase (BCKD) were assayed in mitochondria isolated from kidneys of rats. Rates of transamination of valine and oxidation of keto acids alpha-ketoisocaproate (KIC) or alpha-ketoisovalerate (KIV) were estimated using radioactive tracers of the appropriate substrate from amounts of 14C-labeled products formed (14CO2 or [1-14C]-keto acid). Because of the high mitochondrial BCAT activity, an amino acceptor for BCAT, alpha-ketoglutarate (alpha-KG) or KIC, was added to the assay medium when valine was the substrate. Rates of valine transamination and subsequent oxidation of the KIV formed were determined with 0.5 mM alpha-KG as the amino acceptor; these rates were 5- to 50-fold those without added alpha-KG. Rates of CO2 evolution from valine also increased when KIC (0.01-0.10 mM) was present; however, with KIC concentrations above 0.2 mM, rates of CO2 evolution from valine declined although rates of transamination continued to rise. When 0.05 mM KIC was added to the assay medium, oxidation of KIC was suppressed by inclusion of valine or glutamate in the medium. When valine was present KIC was not oxidized preferentially, presumably because it was also serving as an amino acceptor for BCAT. These results indicate that as the supply of amino acceptor, alpha-KG or KIC, is increased in mitochondria not only is the rate of valine transamination stimulated but also the rate of oxidation of the KIV formed from valine.(ABSTRACT TRUNCATED AT 250 WORDS)

Transamination of branched-chain keto acids by isolated perfused rat kidney.

1978 ◽  
Vol 235 (1) ◽  
pp. E47
Author(s):  
W E Mitch ◽  
W Chan
Keyword(s):  
Amino Acids ◽  
Rat Kidney ◽  
Branched Chain Amino Acids ◽  
Keto Acid ◽  
Branched Chain Amino Acid ◽  
Keto Acids ◽  
Perfused Rat Kidney ◽  
Branched Chain ◽  
Branched Chain Keto Acids ◽  
Isolated Rat

Isolated rat kidney perfused without substrate released serine, glycine, and taurine, and substantially smaller amounts of other amino acids. When branched-chain keto acids were added, the corresponding amino acids were released at rates amounting to 15-25% of keto acid disappearance. Perfusion with 2 mM alpha-keto-isovalerate or alpha-keto-beta-methylvalerate caused an increased glucose release amounting to 18-23% of keto acid disappearance. The activity of branched-chain amino acid transferase (BATase) was significantly stimulated by perfusion with the analogue of leucine, but not by perfusion with alpha-ketoglutarate, the analogues of valine or isoleucine, or with leucine itself. These findings document that the kidney converts branched-chain keto acids in part to the corresponding amino acids and suggest that the keto analogue of leucine may be involved in the control of renal BATase activity, thereby indirectly regulating the metabolism of branched-chain amino acids.

BRANCHED-CHAIN ALPHA-KETO ACID EXCHANGE ACROSS THE PORTAL-DRAINED VISCERA AND HINDLIMB OF FED AND FASTED STEERS

1984 ◽  
Vol 64 (5) ◽  
pp. 276-277 ◽  
Author(s):  
R. J. EARLY ◽  
J. R. THOMPSON ◽  
R. J. CHRISTOPHERSON ◽  
G. W. SEDGWICK
Keyword(s):  
Key Words ◽  
Keto Acid ◽  
Keto Acids ◽  
Branched Chain ◽  
Net Release ◽  
Acid Exchange

Fasting (6 day) steers increased (P < 0.05) arterial alpha-ketoisocaproate concentration and decreased (P < 0.05) the net release of alpha-ketoisovalerate from the portal-drained viscera. The net release of all three branched-chain alpha-keto acids from the hindlimb was decreased (P < 0.05) after fasting. Key words: Branched-chain, alpha-keto acids, steers

Glucocorticoid-mediated activation of muscle branched-chain alpha-keto acid dehydrogenase in vivo

1987 ◽  
Vol 252 (3) ◽  
pp. E396-E407 ◽  
Author(s):  
K. P. Block ◽  
W. B. Richmond ◽  
W. B. Mehard ◽  
M. G. Buse
Keyword(s):  
Skeletal Muscle ◽  
Amino Acid ◽  
Active Enzyme ◽  
Acid Oxidation ◽  
Enzyme Complex ◽  
Keto Acid ◽  
Amino Acid Oxidation ◽  
Acid Dehydrogenase ◽  
Branched Chain Amino Acid ◽  
Branched Chain

Muscle branched-chain alpha-keto acid dehydrogenase, the rate-limiting enzyme for branched-chain amino acid oxidation in skeletal muscle, was measured after treatment of rats with glucocorticoids. Cortisone treatment (10 mg X 100 g body wt-1 X day-1 for 2–5 days) resulted in an approximate doubling of the percentage of active enzyme. To further characterize this effect, the enzyme complex was measured 4 h after the intraperitoneal injection of 6 alpha-methylprednisolone, a water-soluble glucocorticoid with rapid onset effects. The percentage of active enzyme increased linearly as the dose of methylprednisolone was increased from 0.125 to 12.5 mg/100 g body wt, while total enzyme activity was unchanged. Administration of insulin with glucose had no significant effect on the activity of the enzyme. However, treatment of rats with insulin and glucose after methylprednisolone administration partially blocked branched-chain alpha-keto acid dehydrogenase activation. The activity of the enzyme complex was correlated with the concentration of leucine in plasma and muscle. Activation of skeletal muscle branched-chain alpha-keto acid dehydrogenase by increased glucocorticoids may play a role in the acceleration of branched-chain amino acid oxidation observed during severe stress.

scholarly journals Influence of dietary leucine content on the activities of branched-chain amino acid aminotransferase (EC 2.6.1.42) and branched-chain α-keto acid dehydrogenase (EC 1.2.4.4) complex in tissues of preruminant lambs

1988 ◽  
Vol 59 (3) ◽  
pp. 475-483 ◽  
Author(s):  
Isabelle Papet ◽  
Nadia Lezebot ◽  
Francoise Barre ◽  
Maurice Arnal ◽  
Alfred E. Harper
Keyword(s):  
Amino Acid ◽  
Longissimus Dorsi ◽  
Keto Acid ◽  
Amino Acid Catabolism ◽  
Longissimus Dorsi Muscle ◽  
Acid Dehydrogenase ◽  
Branched Chain Amino Acid ◽  
Dorsi Muscle ◽  
Branched Chain ◽  
Low Rate

1. Branched-chain amino acid aminotransferase (EC 2.6.1.42; BCAAT) and branched-chain α-keto acid dehydrogenase (EC 1.2.4.4; BCKDH) activities were measured in preruminant lamb liver, longissimus dorsi muscle, kidney, jejunum and adipose tissue, 2 h after a meal with or without an excess of leucine.2. Skeletal muscle contained about 70% of the total basal BCAAT activities of the tissues studied whereas liver contained about 60% of the total BCKDH activities of these tissues.3. BCAAT activities were very low in preruminant lamb tissues. BCKDH was more phosphorylated in tissues of preruminant lambs than in rats, especially in liver. These low catalytic potentialities might contribute to a low rate of branched-chain amino acid catabolism in sheep.4. Ingestion of an excess of leucine led to an increase in liver and jejunum BCAAT activities and activation of BCKDH in jejunum.

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