Immediate and Prolonged Effects of Hydrocortisone on the Free Amino Acids of Rat Skeletal Muscle.

Ryan, Wayne L.; Carver, Michael J.

doi:10.3181/00379727-114-28808

Cited by 31 publications

(9 citation statements)

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“…Nevertheless, examination of their data reveals higher mean plasma levels during cortisol treatment only in the case of alanine, at each of three time periods examined (24 h, 1-3 days, and 3-5 days). In acute experiments, a single dose of glucocorticoid has been observed to increase plasma alanine concentration in children (29) and in rats (30). The present data demonstrate a specific elevation in plasmia alanine after 3 days of dexamethasone treatment.…”

Section: Discussionsupporting

confidence: 63%

Influence of Glucocorticoids on Glucagon Secretion and Plasma Amino Acid Concentrations in Man

Wise¹,

Hendler²,

Felig³

1973

J. Clin. Invest.

241

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A B S T R A C T Plasma concentrations of glucagon, insulin, glucose, and individual plasma amino acids were measured in normal nonobese and obese subjects before and after 3 days of dexamethasone treatment (2 mg/ day) and in patients with Cushing's syndrome. The subjects were studied in the basal postabsorptive state and following the infusion of alanine (0.15 g/kg) or ingestion of a protein meal.In nonobese subjects dexamethasone treatment resulted in a 55% increment in basal glucagon levels and in a 60-100% increase in the maximal glucagon response to alanine infusion or protein ingestion. In obese subjects, basal glucagon rose by 110% following dexamethasone, while the response to alanine increased fourfold. In patients with Cushing's syndrome basal glucagon levels were 100% higher and the glucagon response to alanine infusion was 170% greater than in normal controls. Dexamethasone treatment in normal subj ects resulted in a 40% rise in plasma alanine concentration which was directly proportional to the rise in basal glucagon. The remaining 14 amino acids were unchanged. In the patients with Cushing's syndrome alanine levels were 40% higher than in normal controls and were directly proportional to basal glucagon concentrations. No other plasma amino acids were significantly altered in the group with Cushing's syndrome.It is concluded that (a) glucocorticoids increase plasma glucagon concentration in the basal state and in response to protein ingestion or aminogenic stimulation; (b) this effect of glucocorticoids occurs in the This work was presented in part at the 65th Annual

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Section: Discussionsupporting

confidence: 63%

Influence of Glucocorticoids on Glucagon Secretion and Plasma Amino Acid Concentrations in Man

Wise¹,

Hendler²,

Felig³

1973

J. Clin. Invest.

241

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“…The placenta is an active metabolic organ with significant oxygen requirements (3) and involved in the synthesis of large amounts of protein. Similar amino acid concentrations have been reported in other active metabolic organs such as liver, brain, and muscle (1, 14,15).…”

Section: L-leucine L-aspartic Acid Discussionsupporting

confidence: 55%

Transfer of Amino Acids across the In Vitro Perfused Human Placenta

Schneider

Dancis

1979

Pediatr Res

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SummaryAmino acid transfer across human placenta has been studied in an in vitro perfusion system. Transfer rates from maternal to fetal circuit of 12 amino acids were about the same when there was a downhill gradient permitting diffusion and active transport. This was termed "maximal transfer rate." Cystine, aspartic acid, and glutamic acid were transferred a t approximately half the rate of the others under these conditions. Measurement of exchange rates with radioactive tracers and with equimolar concentration of amino acids on both sides of the membrane provided a close estimate of maximal transfer rate. Fetal nutrition requires active transfer against a gradient. The rate of active transfer is a fraction of the exchange rate.The ability to establish a transplacental gradient by perfused placenta was investigated with the maternal circuit open and fetal circuit closed (recirculated). The fetal to maternal concentration ratio for D-leucine and antipyrine was 1.0, for L-leucine, 1.5, indicating a stereospecific transport mechanism for leucine. Cradients of 1.56 + 0.11 and 1.62 +. 0.10 were demonstrated for Lalanine and L-lysine, respectively. The establishment of transplacental gradients is a placental function, requiring no assistance using a variety of experimental techniques and experimental animals. Studies in the human have been extremely limited. Slices and fragments of human placenta have been used in vitro to measure amino acid transport (1 I, 12, 16, 19), but the pertinence of the observations to transplacental transport is uncertain. Page et al. (13) have infused D-and L-histidine into several mothers shortly before delivery and have measured the relative concentrations of the stereoisomers in the cord blood at birth. They deduced that L-histidine was transferred more rapidly than the D-isomer. Gaull et al. (7) have studied transfer rates of the sulfur-amino acids during the second trimester in elective abortions.For the past several years, we have been studying transplacental transport by perfusing a n isolated cotyledon of human placenta. Independent maternal and fetal circulations are established permitting the investigation of transfer in either direction. This technique has now been applied to the study of amino acid transport in a n attempt to answer such fundamental questions as the relation of exchange rates to net transfer, the pertinence of in vitro placental uptake studies to transplacental transport, the polarity of the placental membrane, and the possible reserve functions of the large intraplacental concentrations of amino acids. from maternal or fetal factors.The ratios of the exchange rates for the L and D-isomers were MATERIALS AND METHODS determined as a measure of the active, stereospecific transport system. The L:D ratio from the maternal to fetal circulation for PERFUSION TECHNIQUE leucine was 1.64 f 0.19, for alanine 1.78 + 0.49. In the reverse ~h~ technique of dual perfusion of the human placental cotydirection, the ratio for leucine was 1.03. The placental membrane ledon ha...

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“…Previous studies suggested that these differences appear to be time-related (36 The initial elevation induced by glucocorticoids is con-sistelit with an increase in amino acid mobilization from the peripheral tissues (37). A feasible explanation for the subsequent depression is the decreased release of amino acids from muscle (the body's principal protein store) coincident with the secondary hyperinsulinemia (38) that developed after glucocorticoid administration.…”

Section: Resultsmentioning

confidence: 99%