Impact of 2H and 18O pool size determinations on the calculation of total energy expenditure

Measurement of total energy expenditure using [2H,18O] water requires both accurate and precise determination of the rates of disappearance of 2H and 18O from body water over time and determination of the 2H and 18O pool sizes. However, the impact of the isotopic determination of body water upon the determination of energy expenditure is often overlooked. For measurement of total body water per se, the delay after administration before sampling body fluids becomes important, and saliva sampling can be used to resolve the timing of early samples for body water determination. For energy expenditure measurement per se, linear regression can be used to define the initial dilution. Because the hydrogen tracer dilutes into a pool significantly larger than body water pool per se due to the presence of labile hydrogens, a correction to the isotope pool size must be applied. The theoretical calculations of the exchangeable hydrogen pool presented here suggest that the hydrogen pool size is < 3% greater than the body water pool and data are provided to support this idea. Finally, the two approaches used to define the body water pool space contribution to the calculation of energy expenditure using 2H2(18)O are reviewed. Using a pool size based upon the average of the two pool spaces limits the effect of pool size error in the calculation of energy expenditure.

Intraarticular lidocaine versus intravenous analgesic for reduction of acute anterior shoulder dislocations. A prospective randomized study

We performed a prospective, randomized study to evaluate the use of injected lidocaine as an anesthetic for closed reduction of acute anterior shoulder dislocations. Thirty consecutive patients who presented at the emergency department with acute anterior shoulder dislocations were randomly placed in one of two groups. One group received an intraarticular injection of 20 ml of 1% lidocaine and the other group, intravenous injections of morphine sulfate and midazolam. The groups were compared regarding time of reduction maneuver, difficulty of reduction, subjective pain, complications, and total time spent in the emergency department. The lidocaine provided adequate anesthesia and secondary relief of muscle spasm in 15 of 15 (100%) patients. When compared with the intravenous sedation group, the lidocaine group showed no statistically significant difference in time for reduction maneuver, difficulty of reduction, or subjective pain. The lidocaine group had no complications and had a statistically significant shorter emergency department visit when compared with the intravenous sedation group (mean, 78 minutes versus 186 minutes; P = 0.004). Lidocaine provides excellent anesthesia for patients with uncomplicated anterior shoulder dislocations and can be very beneficial when sedation is contraindicated. Lidocaine injections also proved to be cost effective in our institution, reducing total costs by as much as 62%.

Arthroscopic suture fixation of displaced tibial eminence fractures

The purpose of this article is to describe a technique for arthroscopic reduction and suture fixation of avulsion fractures of the tibial eminence involving the anterior cruciate ligament (ACL). Six patients (five type III, one type II) with tibial eminence fractures underwent arthroscopic evaluation when closed reduction after aspiration failed to yield an anatomic reduction. The study population was composed of five males and one female. Average age was 24 years (range 16-36). One fracture (type II) was easily reduced after manipulating the interposed anterior horn of the lateral meniscus. In five patients the fragment was stabilized with multiple sutures. The technique involved arthroscopic placement of multiple sutures of 2-0 polydioxanone suture (PDS) into the base of the ACL pulled through a tibia drill hole and tied onto a 4.5-mm screw post. Patients were placed in a standard postoperative ACL protocol. All fractures demonstrated radiographic healing by 8 weeks, and no patients had subjective complaints of instability at 1 year. All patients obtained full extension intraoperatively, and only one patient lost 2 degrees of terminal extension at latest follow-up. Arthroscopic reduction and suture fixation of avulsion fractures of the tibial eminence restores the length of the ACL, provides stable fixation promoting early motion with minimal morbidity, and does not require a second operation for metal removal.

Insulin selectively attenuates breakdown of nonmyofibrillar proteins in peripheral tissues of normal men

The role of insulin to control protein synthesis and degradation in the human leg and forearm was investigated in eight healthy individuals. The glucose clamp technique with simultaneous infusion of crystalline amino acids were used to create hyperinsulinemia (100-120 mU/l) in combination with euglycemia and elevated plasma concentrations of amino acids (> 4 mmol/l). A primed constant infusion with L-[U-14C]tyrosine and L-[phenyl-2H5]phenylalanine was used for simultaneous measurements of the disposal (protein synthesis) and the release (protein degradation) of tyrosine and phenylalanine, respectively, across the leg and forearm before and during hyperinsulinemia. The balance of 3-methylhistidine was also determined as a measure of muscle breakdown. Insulin stimulated tissue glucose and net amino acid uptake across the arm and leg tissues, whereas the disposal of both tyrosine and phenylalanine (protein synthesis) was not stimulated across the arm and the leg during hyperinsulinemia. The release of tyrosine and phenylalanine was significantly decreased from both leg and arm tissues (protein degradation) in response to insulin. However, the release of 3-methylhistidine from skeletal muscles was totally unaffected by hyperinsulinemia. We conclude that it is unlikely that insulin contributes to the normal stimulation of protein synthesis during feeding in humans and that insulin has no effect on breakdown of the large myofibrillar protein pool in skeletal muscles in unstressed individuals.

Whole body and splanchnic leucine, phenylalanine, and glucose kinetics during endotoxemia in humans

To examine the whole body and splanchnic tissue substrate handling during endotoxemia, an intravenous bolus of endotoxin was given to six healthy volunteers during primed, continuous infusions of [1-13C]leucine, [ring-2H5]phenylalanine, and [6,6-2H2]glucose. Whole body protein breakdown, based on whole body Leu and Phe appearance rates (Ra), increased in response to endotoxin given at time 0 (RaLeu 77 +/- 2 mol.kg-1 x h-1, t = 0 h; 88 +/- 6, t = 4 h; P < 0.05) (RaPhe 39 +/- 2 mol.kg-1 x h-1, t = 0; 46 +/- 3, t = 4 h; P < 0.05). Splanchnic amino acid balance (Bal) increased (BalLeu 7 +/- 4 mol.kg-1 x h-1, t = 0; 21 +/- 5, t = 2 h; P < 0.05) (BalPhe 3 +/- 2 mol.kg-1 x h-1, t = 0; 16 +/- 4, t = 2 h; P < 0.05) and can be accounted for by increased splanchnic uptake (Rd) of Phe and Leu (RdLeu 21 +/- 3 mol.kg-1 x h -1, t = 0; 37 +/- 7, t = 120 min; P < 0.05) (RdPhe 10 +/- 3 mol.kg-1 x h-1, t = 0; 24 +/- 5, t = 120 min; P < 0.05). Splanchnic conversion of Leu to ketoisocaproate increased with endotoxin administration (0.7 +/- 0.6 mol.kg-1 x h-1, t = 0; 8 +/- 3, t = 360 min; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of endurance training on plasma free fatty acid turnover and oxidation during exercise

Plasma free fatty acid (FFA) levels tend to be lower and the plasma lipolytic hormone response to prolonged exercise of the same intensity is blunted after endurance exercise training. To determine whether training elicits a corresponding decrease in plasma FFA turnover and metabolism during prolonged exercise, we measured plasma [1-13C]palmitate kinetics and oxidation and respiratory gas exchange in 13 subjects during the latter portion of a 90- to 120-min bout of cycle ergometer work performed before and after 12 wk of alternate-day cycling and running. Training increased total fat oxidation during prolonged exercise by 41% (P < 0.005). However, for the final 30-60 min of the cycle ergometer protocol, the rate of 13CO2 production from [1-13C]palmitate oxidation was 27% lower (P < 0.05), the rate of palmitate turnover was 33% less (P < 0.05), and plasma FFA and glycerol concentrations were 32 and 20% lower (P < 0.05), respectively, than in the untrained state. Thus endurance exercise training results in decreased plasma FFA turnover and oxidation during a 90- to 120-min bout of submaximal exercise because of a slower rate of FFA release from adipose tissue.

[13C]cholesterol as a tracer for studies of cholesterol metabolism in humans

The investigation of cholesterol metabolism in humans would be facilitated by the availability of a tracer that is not radioactive. However, to be useful such a tracer must be detectable in the large pool of body cholesterol over an extended time. To meet these requirements we used synthetic [23,24,25,26,27-13C5]cholesterol with detection by isotope ratio mass spectrometry (IRMS), a technique in which the ratio of 13CO2/12CO2 can be determined with high precision in the combustion products of a biological sample. [13C]cholesterol (65 mg) and [14C]cholesterol (15 microCi) were solubilized in Intralipid and injected simultaneously (IV) into three normal subjects, and plasma samples were obtained over the ensuing 10 weeks. Cholesterol was isolated from plasma and either counted for radioactivity or combusted to CO2 and analyzed by IRMS. [14C]cholesterol and [13C]cholesterol tracer concentrations in plasma were very similar. [13C]cholesterol kinetic parameters calculated using a standard two-compartment cholesterol turnover model and a new three-compartment minimal model were 103 +/- 10.5 SD % of those computed from corresponding [14C]cholesterol data. These results show that [13C5]cholesterol can be used as a practical tracer for cholesterol metabolic studies lasting many weeks.

Glucose resistance contributes to diabetes mellitus in cirrhosis

Insulin resistance is a characteristic feature of glucose-intolerant and diabetic cirrhotic patients. The pathogenic factors, however, that are responsible for the development of impaired glucose tolerance in cirrhosis, remain unclear. To examine whether the ability of hyperglycemia per se to enhance glucose uptake (by means of mass-action effect) is impaired in cirrhosis, we measured (insulin-independent) whole-body glucose disposal during hyperglycemia (hyperglycemic clamp studies, +125 mg/dl, in combination with an infusion of somatostatin (500 micrograms/hr), insulin (0.1 mU/kg min) and glucagon (0.5 ng/kg min) to "clamp" hormone levels at baseline), whole-body glucose oxidation (indirect calorimetry) and glucose turnover (prime-continuous infusion of [6,6-2H2-]glucose in a clinically homogeneous group of cirrhotic patients with glucose intolerance (n = 7) or frank diabetes mellitus (n = 7) and in control individuals (n = 7). Fasting plasma glucose concentrations were normal in glucose-intolerant patients but were significantly increased in diabetic patients (158 +/- 19 vs. 87 +/- 2 mg/dl in controls; p < 0.01). Plasma glucose concentrations were clamped at 214 +/- 4 mg/dl in controls, at 212 +/- 4 mg/dl in glucose-intolerant patients and at 287 +/- 19 mg/dl in diabetic patients; plasma insulin and glucagon concentrations were maintained at baseline levels. In the basal state, total-body glucose disposal (which equals basal hepatic glucose output) was normal in glucose-intolerant patients (2.25 +/- 0.11 mg/kg min) but was increased in diabetic patients compared with controls (3.32 +/- 0.26 mg/dl vs. 2.45 +/- 0.10 mg/dl; p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Increased energy expenditure in a patient with diencephalic syndrome

Total energy expenditure, measured in an infant with diencephalic syndrome with doubly labeled water, was 30% to 50% higher than that reported for other healthy infants whose energy expenditure was measured by the same technique and 13% higher than the patient's energy intake. This result suggests that the weight loss and cachexia of the diencephalic syndrome are the result of abnormally increased energy expenditure.

Splanchnic bed utilization of glutamine and glutamic acid in humans

To study the fate of enterally delivered nonessential amino acids, glutamine and glutamate, 14 healthy adults were infused in the postabsorptive state with [2-15N]glutamine and [15N]glutamate for 7 h by intravenous (iv) and nasogastric (ng) tube routes. The amount of enterally delivered tracer that was sequestered by the splanchnic bed on the first pass was 54 +/- 4 and 88 +/- 2% for the [2-15N]glutamine and [15N]glutamate tracers, respectively. Only 46 and 12% of the ng glutamine and glutamate tracers entered systemic blood, respectively. The relative amount of 15N transferred from glutamate to glutamine, the transaminating amino acids leucine, isoleucine, valine, and alanine, and to proline was significantly higher when the [15N]glutamate was infused by the ng vs. iv route. The same was also true for [2-15N]glutamine, which presumably transferred 15N after it was converted to glutamate. Thus we conclude that the splanchnic bed sequesters over one-half of the glutamine and almost all of the glutamate delivered to it in the postabsorptive state. There is production of transaminating amino acids in the splanchnic bed, and the splanchnic bed produces simultaneously both glutamine from glutamate and glutamate from glutamine.

Effects of protein restriction and acute refeeding on leucine and lysine kinetics in young men

To explore the effects of altered protein intake on the uptake and utilization of dietary amino acids in human subjects, six healthy male Massachusetts Institute of Technology students were studied during three dietary periods each of 9 days, with tracer infusion studies conducted on days 8 and 9. During one period the diet provided a generous protein intake (1.5 g.kg-1.day-1) and during the other two a low-protein intake (0.1 g.kg-1.day-1). Tracer infusions (fed state) were given while subjects received either a liquid formula, supplying the prior protein intake or (on day 9) a generous intake. Combinations of [2H3]Leu and [13C]Leu and of [15N]Lys and [2H4]Lys were given via continuous intravenous or intragastric infusion for 4 h to estimate leucine kinetics and the first-pass splanchnic uptake of tracer. Dietary-induced changes in leucine flux and oxidation were similar irrespective of the tracer and/or route of administration and sampled pool (leucine or KIC) used for calculation. Estimates of absolute changes in the rates of leucine disappearance via nonoxidative metabolism (protein synthesis) and of appearance via protein breakdown depended on the route of [13C]Leu administration. However, it appears that both altered rates of protein synthesis and breakdown contribute to the adaptations required in the body nitrogen economy when protein intakes are restricted and subsequently resupplied. From the intragastric [13C]Leu protocol, the first-pass splanchnic uptake of tracer was the same (approximately 30%) for generous, low-protein, and refed conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

A multivariate example of case-cohort analysis: neonatal mortality in Switzerland, 1979-81

A study of all births in Switzerland during the years 1979-81 is used to illustrate the advantages of the case-cohort design for this epidemiologic analysis of neonatal mortality. The example shows that familiar associations between infant mortality and explanatory variables such as sex and weight at birth can be precisely estimated using only a sample from the full cohort.

The donation cycle: a framework for the measurement and analysis of blood donor return behaviour

The donation cycle represents a new framework for the measurement of blood donor return behaviour. Because it is based on the interval between successive donation attempts, it is more efficient than previously reported methods and the resulting data can be analysed using the statistical techniques for interval data. To illustrate the merits of this quantitative approach to the study of blood donor behaviour, the donation cycle framework is used to analyse the interval between the first and second donation attempts in a random sample (n = 5,183) of type 0, whole blood donors from the Gulf Coast Regional Blood Center. Simple statistical tools such as the log-rank test are employed to describe and to evaluate relative differences in the return behaviour of Rh-negative and Rh-positive donors. The analysis indicates that Rh-negative donors are significantly (p < 0.001) more likely than Rh-positive donors to attempt to donate on a second occasion. Kaplan-Meier estimates of the survival function of these first-time donors reveal marked elevations in the rate of return exactly 52 weeks after the initial donation. The donation cycle paradigm provides transfusion researchers with quantitative tools which are essential for designing statistically efficient, prospective intervention studies. By using the knowledge which such studies could provide, blood banks might be better able to manage donor return behaviour and thereby the safety of the blood supply.

Splanchnic bed utilization of leucine and phenylalanine in humans

To study the fate of enterally delivered essential amino acids, leucine and phenylalanine, 14 healthy adults were infused in the postabsorptive state with [1-13C]leucine, [5,5,5-2H3]leucine, and [phenyl-2H5]phenylalanine for 7 h in a crossover design by intravenous and nasogastric tube routes. The amount of enterally delivered tracer that was sequestered by the splanchnic bed on the first pass was 21 +/- 1, 17 +/- 3, and 29 +/- 2 for the [13C]leucine, [2H]leucine, and [2H]phenylalanine tracers, respectively. Less than 2% of the nasogastric [1-13C]leucine tracer was oxidized on the first pass. We estimate that 40% of the nasogastric leucine tracer that was sequestered on the first pass was converted to alpha-ketoisocaproate and released, and 50% was incorporated into newly synthesized proteins. Assuming that less phenylalanine is incorporated into protein than leucine because of the lower abundance of phenylalanine in protein compared with leucine, we estimate that 80% of the extracted nasogastric phenylalanine tracer was converted to tyrosine. The study design also indicated a significant effect of duration of tracer infusion on the results, presumably due to recycling of tracer from rapidly turning over protein.

Discrepancy between self-reported and actual caloric intake and exercise in obese subjects

BACKGROUND AND METHODS

Some obese subjects repeatedly fail to lose weight even though they report restricting their caloric intake to less than 1200 kcal per day. We studied two explanations for this apparent resistance to diet--low total energy expenditure and underreporting of caloric intake--in 224 consecutive obese subjects presenting for treatment. Group 1 consisted of nine women and one man with a history of diet resistance in whom we evaluated total energy expenditure and its main thermogenic components and actual energy intake for 14 days by indirect calorimetry and analysis of body composition. Group 2, subgroups of which served as controls in the various evaluations, consisted of 67 women and 13 men with no history of diet resistance.

RESULTS

Total energy expenditure and resting metabolic rate in the subjects with diet resistance (group 1) were within 5 percent of the predicted values for body composition, and there was no significant difference between groups 1 and 2 in the thermic effects of food and exercise. Low energy expenditure was thus excluded as a mechanism of self-reported diet resistance. In contrast, the subjects in group 1 underreported their actual food intake by an average (+/- SD) of 47 +/- 16 percent and overreported their physical activity by 51 +/- 75 percent. Although the subjects in group 1 had no distinct psychopathologic characteristics, they perceived a genetic cause for their obesity, used thyroid medication at a high frequency, and described their eating behavior as relatively normal (all P < 0.05 as compared with group 2).

CONCLUSIONS

The failure of some obese subjects to lose weight while eating a diet they report as low in calories is due to an energy intake substantially higher than reported and an overestimation of physical activity, not to an abnormality in thermogenesis.

Purification and characterization of cyanide hydratase from the phytopathogenic fungus Gloeocercospora sorghi

Previous studies have demonstrated that fungal pathogens of cyanogenic plants produce cyanide hydratase (CHT, EC 4.2.1.66), which converts HCN to formamide. Production of CHT in these fungi is thought to be a means of circumventing cyanide toxicity, and CHT is thus believed to be an important pathogenicity trait. In the present study, 13 species of fungi were assayed for CHT production, and all 7 species that were pathogens of sorghum, a cyanogenic plant, produced this enzyme. CHT was purified to apparent homogeneity from one of these sorghum pathogens, Gloeocercospora sorghi. The enzyme had a Km of 12 mM for KCN. Enzymatically functional CHT was obtained only as a large molecular entity of greater than 300 kDa. However, a polypeptide of approximately 45 kDa was identified as the only component of purified CHT detectable by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The 45-kDa polypeptide band could be resolved into three isozymes of pI 6.1, 6.3, and 6.5. Antibodies raised against the 45-kDa polypeptide inhibited the G. sorghi CHT activity and showed high specificity in Western blots to a polypeptide of approximately the same size. The evidence suggests that functional G. sorghi CHT is an aggregated protein that consists of 45-kDa polypeptides. A CHT with similar properties was also found in the fungus Colletotrichum graminicola, another pathogen of sorghum.

A mass spectrometric method for measuring glycerol levels and enrichments in plasma using 13C and 2H stable isotopic tracers

The stable isotope tracer [1,1,2,3,3,-2H5]glycerol has been commonly used as a tracer to measure glycerol kinetics and lipolysis in vivo. The method for measuring samples using the trimethylsilyl derivative and electron impact gas chromatograph-mass spectrometry retains only three of the five deuteriums, resulting in the possibility of incorrectly identifying the whole glycerol tracer molecule. This reports preparation of glycerol as the heptafluorobutyrl derivative and measurement by negative ion chemical ionization gas chromatography-mass spectrometry to produce a derivative with an intense molecular ion that retains all five deuterium labels. Thus the heptafluorobutyrl derivative analyzed by negative ion mass spectrometry overcomes the problems associated with fragmentation and loss of the isotopic label. Glycerol concentration using a labeled internal standard can be determined in plasma with a precision of 3%. Nanomole amounts of glycerol can be analyzed for 13C or 2H enrichments with a precision of +/- 0.14 mol% excess isotope. This simple, sensitive method for measuring glycerol levels and stable isotopic enrichment in plasma uses a simple extraction procedure and requires a minimal volume of plasma (less than 300 microliters).

Effect of leucine on amino acid and glucose metabolism in humans

Leucine has been reported to be an important regulator of protein metabolism. We investigated the effect of intravenous infusion of L-leucine versus saline on amino acid metabolism in eight healthy human subjects. Plasma concentrations of amino acids were measured and protein turnover was estimated using L-(1-13C)lysine and L-(3,3,3,-2H3)leucine as tracers. Glucose kinetics were measured using D-(6,6-2H2)glucose as a tracer. Leucine infusion increased the plasma leucine concentration from 103 +/- 8 to 377 +/- 35 mumol/L (P less than .01). Plasma concentrations of essential amino acids, including threonine, methionine, isoleucine, valine, tyrosine, and phenylalanine were significantly decreased by leucine infusion. Leucine infusion did not change lysine flux significantly (108 +/- 4 during saline v 101 +/- 4 mumol/kg/h-1 during leucine infusion), but decreased lysine oxidation (13.2 +/- 0.9 v 10.7 +/- 1 mumol/kg/h, P less than .05) and endogenous leucine flux (from 128 +/- 4 to 113 +/- 7 mumol/kg/h, P less than .05) when plasma (2H3) ketoisocaproate (KIC) was used for calculation. During leucine infusion, the (2H3) KIC to (2H3) leucine plasma enrichment ratio increased from 0.76 +/- 0.02 to 0.88 +/- 0.01 (P less than .001), while estimation of leucine flux using plasma (2H3) leucine showed no change in endogenous leucine flux. Leucine infusion decreased hepatic glucose production and metabolic clearance of glucose, but did not change plasma concentrations of glucose, insulin, C-peptide, glucagon, epinephrine, norepinephrine, or free fatty acids. We conclude that leucine spares glucose and lysine catabolism and decreases plasma concentrations of essential amino acids.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of dietary protein intake on glutamine and glutamate nitrogen metabolism in humans

The response of glutamine and glutamate kinetics were studied in five healthy young adult men on diets containing deficient (0.1), adequate (0.8), or surfeit (2.2 g.kg-1.d-1) amounts of protein. Glutamate, glutamine, and phenylalanine kinetics were measured in the postabsorptive state at the end of each diet period. Urinary urea and ammonia excretion correlated with protein intake (the sum of the two was 2.1 +/- 0.2, 5.7 +/- 0.3, and 11.9 +/- 1.2 g N g.kg-1.d-1 for the respective 0.1, 0.8, and 2.2 g.kg-1.d-1 protein intakes). Glutamate and glutamine concentrations varied inversely with protein intake. Phenylalanine concentrations and phenylalanine flux did not change significantly with the changing protein intake. Both glutamate and glutamine fluxes varied inversely with protein intake (glutamate flux was 177 +/- 15, 120 +/- 10, and 125 +/- 11 mumol.kg-1.h-1 and glutamine flux was 373 +/- 29, 343 +/- 26, and 318 +/- 15 mumol.kg-1.h-1 at the respective 0.1, 0.8, and 2.2 g.kg-1.d-1 protein intakes). These changes in glutamine or glutamate flux in response to alterations in dietary protein intake were attributable to changes in de novo production.

beta-Furfuryl-beta-Glucoside: An Endogenous Activator of Higher Plant UDP-Glucose:(1-3)-beta-Glucan Synthase : Biological Activity, Distribution, and in Vitro Synthesis

In a recent paper (P Ohana, DP Delmer, JC Steffens, DE Matthews, R Mayer, M Benziman [1991] J Biol Chem 266: 13472-13475), we described the purification and structural characterization of beta-furfuryl-beta-glucoside (FG), an endogenous activator of plant UDP-glucose:(1-->3)-beta-glucan (callose) synthase. In the present report, we provide evidence that FG specifically stimulates callose synthase. The effects of FG on the kinetic properties of callose synthase were studied, and we ascertained that FG, or at least a very similar compound, is present in other plant systems. Chemically synthesized alpha-furfuryl-beta-glucoside also stimulates callose synthase, exhibiting a slightly higher K(a) of 80 micromolar, compared with 50 micromolar for FG. In addition, we have identified and partially characterized an enzyme that catalyzes the synthesis of FG using beta-furfuryl alcohol and UDP-glucose as substrates. A model for the regulation of callose synthesis in vivo, involving changes in intracellular compartmentation of FG and Ca(2+), is proposed.

The influence of substrate background on the acute metabolic response to epinephrine and cortisol

The acute metabolic effects of epinephrine and cortisol, as well as the influence of substrate background on the effects of these two hormones were investigated in normal subjects. While receiving a hypocaloric dextrose feeding (50 ng/kg/h) (DEX), the subjects received a 6-hour continuous intravenous infusion of epinephrine (30 ng/kg-min) (EPI), followed by a 6-hour infusion of a combination of epinephrine (30 mg/kg-min) and cortisol (3.0 microgram/kg-min) (EC). The hormone infusion was repeated 1 week after a continuous intravenous feeding regimen (TPN) was begun with a caloric content of 1.5 times the measured metabolic rate. Under both DEX and TPN, EPI produced increased energy expenditure, hyperglycemia, hyperlactic acidemia, and hypoaminoacidemia. Except for a further increase in circulating glucose levels during the DEX condition, these variables were not altered by the addition of cortisol. Epinephrine under both feeding conditions increased lactate efflux from the extremity without changes in peripheral oxygen or glucose uptake. The hypoaminoacidemic response to EPI in the DEX condition was associated with a decrease in extremity efflux of amino acids (-654 +/- 89 nmol/min/100 cm3 tissue at baseline vs -330 +/- 86 nmol/min/100 cm3 for EPI, p less than 0.05). No change in extremity amino acid flux was noted in response to EPI during total parenteral nutrition. Even with addition of cortisol no significant efflux of amino acids above baseline levels was noted in either feeding condition. We therefore conclude that (1) total parenteral nutrition cannot abolish the hypermetabolic or hyperglycemic response to epinephrine and cortisol; (2) increased extremity lactate efflux and lactic acidosis can occur in response to epinephrine without evidence of diminished oxygen delivery to the extremity; and (3) these two hormones are not primary mediators of acute extremity nitrogen loss.