[NT-proBNP measurement on Immulite 2500 (DPC): analytical performance and comparison with Roche Diagnostics and Dade-Behring NT-proBNP immunoassays]. / Dosage du NT-proBNP sur l'Immulite 2500 (DPC): évaluation analytique et comparaison avec les trousses Roche-Diagnostics et Dade-Behring.

The measurement of the N-terminal part of the proBNP (NT-proBNP) may be used to assess the secretion of the B-type natriuretic peptide (BNP), a marker of heart failure. In this study, we have evaluated the NT-proBNP immunoassay proposed by DPC Company for the Immulite 2500 analyzer and compared the results with those obtained with the two other immunoassays respectively commercialized by Roche Diagnostics (Elecsys 2010 analyzer) and Dade-Behring (Dimension RXL). The obtained results show very good general performance of the DPC's technique with a CV inferior to 8% for the values superior to 40 ng/L. The within run CVs are 3.1, 3.5 and 3.5% and the between run CVs are 3.8, 4.7 and 4.8% for the NT-proBNP levels of 151, 1601 and 5255 ng/L, respectively. We found a very good correlation between DPC's and Roche Diagnostics's assays (regression analysis: y = 0.88 x + 25.2 ; r = 0.998) and DPC's and Dade-Behring assays (regression analysis: y = 0.93 x + 16.4 ; r = 0.997). Although a small bias appeared between these assays, similar cut-points may be used to exclude both heart failure in ambulatory patients and cardiac origin in acute dyspnea.

[Cardiac troponin I and CK-MB mass after cardiac surgery with cardiopulmonary bypass]. / Troponine Ic et CK-MB masse en chirurgie cardiaque sous circulation extracorporelle.

Cardiac troponin I (cTnI) assay is used in the diagnosis of myocardial infarction after cardiac surgery. Variations in the cut-off value have been reported even with the same assay method. The aim of this work is to investigate the release profile of cTnI and CK-MB mass after cardiac surgery and to determine the cut-off value of cTnI and CK-MB mass allowing the diagnosis of perioperative myocardial infarction. In patients without postoperative cardiac complication, the cTnI peak was observed 24 hours after surgery both in coronary artery bypass grafting and in valve replacement. Moreover, the amount of cTnI released within the three hours after surgery is 2.5 fold higher in valve replacement than in coronary artery bypass grafting. The CK-MB peak was observed 3 hours after surgery in the two surgical procedures. In these patients, cTnI and CK-MB concentrations increased with the cross clamp time duration. In patients with postoperative myocardial infarction, the cTnI and CK-MB peaks were observed 24 hours after surgery. Diagnosis of perioperative myocardial infarction can be performed with a sensitivity of 100% at 24 hours with cut-off values of 32 and 7 microg/L for CK-MB and cTnI, respectively, both with Stratus (Dade Behring) and Immulite (DPC) analysers.

Influence of glutamine on cytokine production by human gut in vitro.

BACKGROUND: glutamine modulates cytokine production by immune cells in vitro and protects the gut from experimental enterocolitis, but data on the effect of glutamine on cytokine production in human gut are lacking. AIM: to assess the effect of glutamine pre-treatment in vivo and in vitro on cytokine production by intestinal mucosa. METHODS: nine fasted volunteers received either enteral glutamine or saline over 6 h in a cross-over design. Duodenal biopsies were cultured for 24 h with or without glutamine. Cytokine content of culture media was analysed by ELISA, and the expression of cytokine mRNA in biopsies was assessed by semi-quantitative RT-PCR. RESULTS: glutamine given in vivo and in vitro significantly decreased IL-6 [1.4 (0.8-8.5) vs 8.9 (1.0-43.9)] and IL-8 production [5.8 (0-51.4) vs. 53.0 (2.5-114.6), pg/mg wet tissue], median (range), both P< or =0.01, in comparison to no glutamine experiments. Glutamine did not influence IL-4 production. IL-1beta, IL-10 and TNF-alpha were not detectable in culture media. The expression of any cytokine mRNA was not influenced by glutamine. CONCLUSIONS: glutamine reduces pro-inflammatory cytokine production by human intestinal mucosa, probably by a post-transcriptional pathway. Glutamine could be useful to modulate inflammatory conditions with imbalanced cytokine production.

AMP-activated protein kinase counteracted the inhibitory effect of glucose on the phosphoenolpyruvate carboxykinase gene expression in rat hepatocytes.

The effect of AMP-activated protein kinase (AMPK) in the regulation of the phosphoenolpyruvate carboxykinase (PEPCK) gene expression was studied in isolated rat hepatocytes. Activation of AMPK by AICAR counteracted the inhibitory effect of glucose on the PEPCK gene expression, both at the mRNA and the transcriptional levels. It is proposed that a target for AMPK is involved in the inhibitory effect of glucose on PEPCK gene transcription.

Synthesis of interleukin 1beta and interleukin 6 by stimulated rat peritoneal macrophages: modulation by glutamine.

Synthesis and secretion of IL-1beta and IL-6 were compared in LPS-stimulated rat peritoneal macrophages, and the effect of glutamine studied. LPS induced a parallel increase in mRNA and synthesis of IL-1beta and IL-6. IL-1beta accumulated mainly in the cytosol and IL-6 in the culture medium. Glutamine addition increased the synthesis of both cytokines, but the overall production (intra-+extracellular) of IL-1beta increased two-fold, although that of IL-6 increased only 1.3-fold. The influence of glutamine is discussed.

Cell swelling activates STAT1 and STAT3 proteins in cultured rat hepatocytes.

In this paper, we demonstrated that in cultured rat hepatocytes cell swelling induced the activation of STAT1 and STAT3 proteins without any effect on STAT4, STAT5 and STAT6 proteins. Cell swelling induced an activation of STAT proteins through an increase in the phosphorylation of the tyrosine residue also phosphorylated by interleukin-6, but without any activation of JAK kinases. The signaling pathway by which cell swelling activated STAT1 and STAT3 is discussed.

Down-regulation of negative acute-phase response genes by hypotonic stress in HepG2 hepatoma cells.

An increased hepatocellular hydration state (HS) that can be induced by hypotonic stress or a high glutamine uptake modulates the transcription of given genes in liver. This could be important in the acute phase (AP) of a systemic inflammation where both HS and glutamine uptake transiently increase in liver. In HepG2 hepatoma cells cultured in conditions of hypotonic stress or a high extracellular glutamine availability, a specifically decreased expression of two human mRNAs, namely those of alphal-microglobulin/bikunin precursor (AMBP) and alpha2-HS-glycoprotein, that are also down-regulated in liver by AP, could be seen. A functional analysis of the AMBP promoter indicated that this hypotonic stress-induced down-regulation takes place at a transcriptional level. In these experiments, the mRNA level and transcription of the glyceraldehyde-3-phosphate dehydrogenase gene that are known to be unmodified in AP did not exhibit any change. Given that hypotonic stress also upregulates the transcription of a liver gene that is also upregulated in AP [Meisse et al. (1998) FEBS Lett. 422, 3463481, the AP-associated increase in hepatocellular HS now appears to participate in the transcriptional control of both sets of genes that are up- or down-regulated in AP.

Cell swelling increased the alpha2-macroglobulin gene expression in cultured rat hepatocytes.

The effect of cell swelling on the expression of the alpha2-macroglobulin (alpha2M) gene was studied in hepatocytes in culture. Hypoosmolarity induced an increase (3-fold increase) in the level of alpha2M mRNA through a corresponding stimulation of the rate of transcription of the alpha2M gene. The addition of raffinose (100 mM) corrected the effect of hypoosmolarity at both mRNA and transcriptional level, demonstrating that cell swelling per se was responsible for the observed effect on the expression of the alpha2M gene. Moreover, the effect of cell swelling was additive to that of interleukin 6, a major mediator of the acute-phase response.

Glutamine and regulation of gene expression in rat hepatocytes: the role of cell swelling.

Glutamine is able to regulate the expression of various genes in rat hepatocytes. This includes genes coding for proteins involved in glutamine utilization, such as argininosuccinate synthetase (ureagenesis) or phosphoenolpyruvate carboxykinase (gluconeogenesis). Moreover, glutamine is also able to stimulate the expression of genes involved in the acute-phase response, such as the alpha 2-macroglobulin gene. The effect of glutamine on the regulation of gene expression may be explained, at least in part, by the cell swelling due to its sodium-dependent transport. The physiological significance of the effect of glutamine is discussed.

Glutamine accelerates interleukin-6 production by rat peritoneal macrophages in culture.

The effect of glutamine on the production of interleukin-6 (IL-6) was studied in rat peritoneal macrophages in culture. A maximal production of IL-6 was measured at 4 h in lipopolysaccharide (LPS)-stimulated macrophages, and addition of glutamine (5 mM) anticipated this increase by 1 h without any increase in the IL-6 mRNA level. The effect of glutamine required the presence of LPS. Thus, glutamine accelerates IL-6 production from the pre-existing mRNA. The effect of glutamine was not mediated by cell swelling since culture of macrophages in hypoosmotic condition decreased the production of IL-6 in the culture medium with a corresponding decrease in the IL-6 mRNA level.

Glutamine inhibits the lowering effect of glucose on the level of phosphoenolpyruvate carboxykinase mRNA in isolated rat hepatocytes.

The expression of phosphoenolpyruvate carboxykinase (P-pyruvate CK) was shown to be decreased by hypoosmolarity and increased by glutamine in perfused liver from fed rats [Newsome, W. P., Warskulat, U., Noe, B., Wettstein, M., Stoll, B., Gerok, W. & Häussinger, D. (1994) Biochem, J. 304, 555-560]. This work was undertaken to specify the mechanisms of glutamine action, using isolated hepatocytes from rats that had been starved for 24 h. At low concentrations (up to 5 mM), glutamine elicited a decrease in the level of P-pyruvate CK mRNA through cell swelling and, at higher concentrations, an increase in the mRNA level was observed. Experiments with combinations of glucose and glutamine or glucose and various amino acids demonstrated that glutamine counteracted the inhibitory effect of glucose on P-pyruvate CK mRNA at a transcriptional, level, and strongly suggested that the amide group of glutamine was involved in this effect. The metabolism of glucose was required for the reinforcement of the apparent stimulatory effect of glutamine, as demonstrated by the use of various sugars. Glucosamine, but not mannosamine, increased the level of P-pyruvate CK mRNA, as did glucose plus glutamine. These results suggest that the pathway leading from glucosamine-6-phosphate production might be responsible, at least partly, for the effect observed on P-pyruvate CK mRNA.

Metabolic changes during early starvation in rats fed a low-protein diet in the postweaning growth period.

Metabolic changes during the first 24 hours of starvation were studied in rats previously adapted for 3 weeks during the postweaning growth period to a low-protein diet using lactalbumin as a dietary protein source. Previous adaptation to a high-quality, low-protein diet reduced the effects of early starvation on the loss of body and liver weight. In rats fed a low-protein diet (6% lactalbumin, LP rats), free triiodothyronine (T3) concentration remained higher than in control rats (13% lactalbumin, C rats) throughout the experiment (+38%, 24 hours), and the plasma insulin concentration, which was lower than in C rats during the first 6 hours (-56%), was not different thereafter. Plasma insulin to glucagon molar ratio was lower (-54%) and liver cyclic adenosine monophosphate (cAMP) concentration was higher (+28%) in LP than in C rats in the fed state, but these were not different at 24 hours of starvation. Plasma glucose concentration was slightly lower in LP than in C rats (-15%) in the fed state, but it was not different in both groups during starvation. Whereas they were unchanged in the fed state, plasma lactate concentration was lower (-57%) and free fatty acid and total ketone body concentrations were higher (+38% and +183%, respectively) in LP than in C rats at 24 hours of starvation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of the new dopaminergic agonist CV 205-502 on plasma prolactin levels and tumour size in bromocriptine-resistant prolactinomas.

Bromocriptine is currently and successfully used for the treatment of pituitary prolactinomas. However, bromocriptine appears unable to normalize plasma prolactin levels in about 10% and to reduce tumour size in one-third of cases. The lack of normalization of plasma prolactin levels in spite of a daily dose of bromocriptine equal to or higher than 15 mg suggests a bromocriptine resistance. We compared the long-term effects of bromocriptine and CV 205-502 (a non-ergot derivative D2 dopamine agonist) on plasma prolactin levels and tumour size in seven bromocriptine-resistant prolactinomas. Bromocriptine reduced significantly (P less than 0.001) plasma prolactin levels (from 2307 +/- 518 to 568 +/- 279 micrograms/l) (conversion to Sl units: 1 microgram/l = 20 mU/l). Visual field defects observed in five patients improved in four. However, CT scan analysis showed a decrease in tumour size in only three patients. Except for transient and minor side-effects at the beginning of the treatment, CV 205-502 was well tolerated in five of seven patients. In the remaining two patients nausea and vertigo occurred with high dosages of CV 205-502 and it was necessary to reduce the daily dose. CV 205-502 lowered plasma prolactin to levels similar to those obtained after bromocriptine therapy in four cases. In the three remaining patients, CV 205-502 was more potent than bromocriptine as demonstrated by the further 90% reduction in plasma levels obtained in one case and by the normalization of plasma prolactin levels in the two other cases. One woman became pregnant during CV 205-502 treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Total and ultrafiltrable plasma magnesium in hyper- and hypoparathyroidism, and in calcium-related metabolic disorders.

Serum total, ultrafiltrable and protein-bound magnesium, and urinary fractional excretion of magnesium were studied in patients with primary hyperparathyroidism (before and after surgery) and in patients with hyperparathyroidism, malignant hypercalcemia and chronic renal failure with or without hemodialysis. Whereas serum total Mg was unchanged in patients with primary hyperparathyroidism, the ultrafiltrable magnesium concentration was higher than in the control group and higher before than after surgery. The total and the ultrafiltrable magnesium concentrations were highly correlated in the overall patients with Ca-related metabolic disorders, suggesting that renal function had no influence on the relation between these two parameters. Moreover, in malignant hypercalcemia, our results suggested that PTH-like peptides might be less effective than PTH in renal handling of Mg as previously described for Ca.

Metabolism of adenosine through adenosine kinase inhibits gluconeogenesis in isolated rat hepatocytes.

In isolated hepatocytes from fasted rats, 0.5 mM adenosine inhibited gluconeogenesis from glutamine, lactate and pyruvate. This inhibition was due to adenosine conversion through adenosine kinase. An increase in ketone body release was only observed in the presence of lactate or pyruvate, and the two phenomena (i.e. inhibition of gluconeogenesis and increased ketone-body release) were linked. With alanine, dihydroxyacetone or serine as substrates, adenosine did not change gluconeogenesis; however, its conversion through adenosine kinase also inhibited gluconeogenesis. With asparagine as substrate, 0.5 mM adenosine increased gluconeogenesis; this increase was due to adenosine conversion through adenosine deaminase. However, adenosine conversion through adenosine kinase inhibited gluconeogenesis from asparagine. Thus, whatever the substrate used, adenosine conversion through adenosine kinase inhibited gluconeogenesis. The inhibitory effect of adenosine on gluconeogenesis cannot be related to the decrease in Pi concentration and to the increase in ATP pool. Beside its effect on gluconeogenesis, adenosine inhibited ketogenesis measured without added substrate; adenosine conversion through adenosine kinase was also involved in the inhibition of ketogenesis.

Influence of 2-chloroadenosine on the nucleotide content of isolated rat hepatocytes.

2-Chloroadenosine is presumably a non-metabolizable analogue of adenosine; however, this compound induced an increase in the enzymatically measured nucleotide content of isolated rat hepatocytes. HPLC separation and spectral analysis of the peaks showed that this increase may be related to the formation of 2-chloro nucleotides and that the 2-chloro nucleotides appeared in the first minutes of the incubation period. These results demonstrate that 2-chloroadenosine may be metabolized by phosphorylation in rat liver cells.

The mechanism by which adenosine decreases gluconeogenesis from lactate in isolated rat hepatocytes.

Incubation of hepatocytes from 24 h-starved rats in the presence of 0.5 mM-adenosine decreased gluconeogenesis from lactate, but not from alanine. The inhibition of gluconeogenesis was associated with a stimulation of ketone-body production and an inhibition of pyruvate oxidation. These metabolic changes were suppressed in the presence of iodotubercidin (an inhibitor of adenosine kinase), but were reinforced in the presence of deoxycoformycin (an inhibitor of adenosine deaminase); 2-chloroadenosine induced no change in gluconeogenesis from lactate. These data indicate that the inhibition of gluconeogenesis by adenosine probably results from its conversion into adenine nucleotides. In the presence of lactate or pyruvate, but not with alanine or asparagine, this conversion resulted in a decrease in the [ATP]/[ADP] ratio in both mitochondrial and cytosolic compartments. Adenosine decreased the Pi concentration with all gluconeogenic substrates.

Influence of beta,gamma-methyleneadenosine 5'-triphosphate and 2-phosphoglycerate on rat liver phosphoglycerate kinase.

The inhibitory action on rat liver phosphoglycerate kinase of structural analogs of the two substrates of this enzyme (beta,gamma- methyleneadenosine 5'-triphosphate for ATP and 2-phosphoglycerate for 3-phosphoglycerate) was studied. In the direction of ADP utilization, the inhibition patterns obtained with beta,gamma-methyleneadenosine 5'-triphosphate are compatible with the reaction mechanism proposed previously (Lavoinne, A., Marchand, J.C., Chédeville, A. & Matray, F. (1983) Biochimie 65, 211-220). In the direction of ATP utilization, the normally observed nonlinear kinetics were changed into linear kinetics in the presence of these substrate analogs. Our results suggest that saturation of the substrate sites induces a conformational change of the enzyme.