Negative association of L-arginine methylation products with oocyte numbers

BACKGROUND

The aim of this study was to determine the concentrations of L-arginine and methylarginines in follicular fluid obtained from women participating in our IVF program and to find clinical correlates of these biochemical parameters.

METHODS

Follicular fluid was obtained from 108 women by ultrasonography guided transvaginal puncture following controlled ovarian hyperstimulation. Follicular fluid L-arginine, asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA) and monomethylarginine (MMA) concentrations were determined with liquid chromatography-tandem mass spectrometry. The integrated index of arginine methylation (arg-MI) was calculated according to the formula: arg-MI = (ADMA + SDMA)/MMA.

RESULTS

There were significant inverse relationships between IVF embryo number and follicular fluid L-arginine (r = -0.507, P < 0.001), ADMA (r = -0.356, P < 0.024), SDMA (r = -0.347, P < 0.028), MMA (r = -0.449, P < 0.004) and to L-arginine/ADMA ratio (r = -0.328, P < 0.031). By contrast, arg-MI was directly related to IVF embryo number (r = 0.426, P < 0.006). Moreover, the number of IVF oocytes was also inversely related to ADMA (r = -0.202, P < 0.037) and MMA (r = -0.384, P < 0.012) and positively to arg-MI (r = 0.450, P < 0.03).

CONCLUSIONS

The elevated levels of follicular fluid l-arginine and methylarginines appear to have an adverse influence on the reproductive processes as reflected by a reduction in the number of oocytes and embryos conceived. In contrast, the integrated methylation index proved to be positively correlated to the above parameters of fertilization.

Elevated levels of asymmetric dimethylarginine in chronic heart failure: a pathophysiologic link between oxygen radical load and impaired vasodilator capacity and the therapeutic effect of allopurinol

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide-dependent vasodilation. In 113 patients with chronic heart failure (CHF) and 26 controls, ADMA level was studied in relation to peripheral blood flow and vasodilator capacity. Further, the effects of allopurinol on concentrations of reactive oxygen species (ROS) and ADMA and peripheral vasodilator capacity were tested in a double-blind design. ADMA level was found to be elevated in CHF patients as compared with controls and increased in parallel with New York Heart Association (NYHA) class and exercise capacity (all P < 0.0001). The level of ADMA predicted resting blood flow (P < 0.05) and postischemic vasodilator capacity (P < 0.001). Sixty eight patients died during the follow-up period. The level of ADMA predicted survival after multivariable adjustment (P = 0.04). Allopurinol reduced uric acid (UA) concentration (P < 0.001) and decreased ROS concentration (allantoin, P < 0.01). Allopurinol lowered ADMA concentration (P = 0.02); postischemic vasodilation as well as endothelium-dependent vasodilation (both P < 0.05) improved. ADMA may be a pathophysiologic factor that is modulated by ROS accumulation and contributes to impaired vascular regulation in CHF.

Low dialysance of asymmetric dimethylarginine (ADMA)--in vivo and in vitro evidence of significant protein binding

BACKGROUND

Increased blood levels of the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) predict cardiovascular mortality in patients with end-stage renal disease. Despite its low molecular weight, available information on the impact of hemodialysis (HD) on ADMA plasma levels is controversial.

METHODS

We assessed plasma concentrations, dialyzer clearance and total amount of ADMA removed in 30 patients with end-stage renal disease during regular HD. In addition, plasma ADMA levels were assessed in 10 patients with acute renal failure treated with extended HD.

RESULTS

Regular HD decreased plasma creatinine (from 774 +/- 42 to 312 +/- 17 micromol/l) and urea (from 24.5 +/- 1.5 to 8.4 +/- 0.5 mmol/l) concentrations significantly (both p < 0.001), whereas plasma ADMA remained unchanged (4.35 +/- 0.19 vs. 4.76 +/- 0.24 micromol/l). ADMA clearance was 92 +/- 6 ml/min, and the total amount removed in the spent dialysate was 37 +/- 4 micromol. The clearances of creatinine (161 +/- 3 ml/min) and of urea (173 +/- 3 ml/min) were significantly higher. Furthermore, even during extended HD, plasma ADMA concentrations did not decrease significantly (1.73 +/- 0.22 vs. 1.63 +/- 0.18 micromol/l).

CONCLUSION

In conclusion, dialysance of ADMA is markedly lower than expected from its molecular weight because of significant protein binding of the substance. Since markedly increased ADMA blood concentrations have been linked to cardiovascular complications due to atherosclerosis in patients with ESRD, new strategies should be evaluated to remove this putative uremic toxin.

Low dialysance of asymmetric dimethylarginine (ADMA) - in vivo and in vitro evidence of significant protein binding

BACKGROUND

Increased blood levels of the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) predict cardiovascular mortality in patients with end-stage renal disease. Despite its low molecular weight, available information on the impact of hemodialysis (HD) on ADMA plasma levels is controversial.

METHODS

We assessed plasma concentrations, dialyzer clearance and total amount of ADMA removed in 30 patients with end-stage renal disease during regular HD. In addition, plasma ADMA levels were assessed in 10 patients with acute renal failure treated with extended HD.

RESULTS

Regular HD decreased plasma creatinine (from 774 +/- 42 to 312 +/- 17 micromol/l) and urea (from 24.5 +/- 1.5 to 8.4 +/- 0.5 mmol/l) concentrations significantly (both p < 0.001), whereas plasma ADMA remained unchanged (4.35 +/- 0.19 vs. 4.76 +/- 0.24 micromol/l). ADMA clearance was 92 +/- 6 ml/min, and the total amount removed in the spent dialysate was 37 +/- 4 micromol. The clearances of creatinine (161 +/- 3 ml/min) and of urea (173 +/- 3 ml/min) were significantly higher. Furthermore, even during extended HD, plasma ADMA concentrations did not decrease significantly (1.73 +/- 0.22 vs. 1.63 +/- 0.18 micromol/l).

CONCLUSION

In conclusion, dialysance of ADMA is markedly lower than expected from its molecular weight because of significant protein binding of the substance. Since markedly increased ADMA blood concentrations have been linked to cardiovascular complications due to atherosclerosis in patients with ESRD, new strategies should be evaluated to remove this putative uremic toxin.

Quantitative determination of piritramide in human serum applying liquid chromatography-two-stage mass spectrometry

A method for the determination of the synthetic narcotic analgesic piritramide in human serum utilizing high-performance liquid chromatography with atmospheric pressure chemical ionization two-stage mass spectrometry (HPLC-APCI-MS-MS) is presented. Pipamperone is used as the internal standard. Serum samples are prepared by liquid-liquid extraction under basic conditions with 1-chlorobutane. The chromatographic separation is achieved on an RP-18 stationary phase applying gradient elution with methanol-0.02% trifluoroacetic acid in water. Detection is carried out in the MS-MS single reaction monitoring mode of the ion-trap mass spectrometer. The limit of detection is 0.3 ng/ml and the calibration covers the range of 1-80 ng/ml. The intra-day RSDs are 6.1 to 7.3% over the calibration range, whereas the inter-day RSDs are 9.6 to 12.8%.

Very sensitive and specific determination of sufentanil in human serum applying liquid chromatography-two stage mass spectrometry

Sufentanil is the most potent synthetic opioid currently in use. Extremely low serum concentrations have to be determined for therapeutic drug monitoring and to support brain death diagnosis by excluding opioid induced coma. The described method utilizes a HPLC-MS-MS system with an electrospray ion source and an ion-trap mass spectrometer. The serum samples were extracted under basic conditions with toluene-2-propanol (10:1, v/v). Chromatographic separation was achieved on a RP-18 70x2 mm column with a 0.02% trifluoroacetic acid in a water-acetonitrile gradient as mobile phase. The limits of detection and quantification are 3 and 10 pg/ml, respectively. At the limit of quantification, the intra-day relative standard deviation of the assay is 12.6% and the inter-day relative standard deviation is 14%.

Sensitive and specific determination of clindamycin in human serum and bone tissue applying liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry

A method for the quantification of clindamycin in human serum and in human bone tissue samples applying high-performance liquid chromatography with atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) is presented. Lincomycin is used as the internal standard. Serum samples are prepared only by protein precipitation with acetonitrile. Bone tissue samples have to be crushed and homogenized in extraction buffer prior to analysis. The chromatographic separation is achieved on an RP-18 stationary phase with 0.02% trifluoroacetic acid in water 60%/ acetonitrile 40% v/v as mobile phase. The limits of quantification are 0.1 microg/ml for serum samples and 0.1 microg/g for bone tissue samples. The coefficients of variation for the assays are 4.48 and 8.41% at the limit of quantification for serum and bone tissue samples, respectively. Bone tissue samples as small as 50 mg can be used.

The effect of anxiety and personality on the pharmacokinetics of oral midazolam

We investigated the relationship between the pharmacokinetic variables of oral midazolam and patients' state/trait anxiety and personality. Twenty-six patients received the standard 15-mg oral dose for anxiolysis on the evening before otorhinolaryngological surgery. Blood samples were taken over a 9-h period after the administration, and the samples were analyzed for concentrations of midazolam and its two main metabolites by using a gas chromatography-mass spectrometry procedure. The pharmacokinetic variables maximum concentration, time to reach the maximum concentration, the elimination half-life, and the area under the curve were calculated from these data. When the patients were divided into groups with respect to their anxiety and personality scores, no significant differences in the pharmacokinetic variables of midazolam could be found. Only small, insignificant changes in the maximum concentrations were found with respect to nervousness and emotionality. We conclude that personality traits and anxiety levels had no effect on the pharmacokinetic variables of midazolam.

IMPLICATIONS

We conclude that personality traits and anxiety levels had no effect on the pharmacokinetic variables of midazolam. Therefore, it is not necessary to obtain anxiety or personality scores to find the proper midazolam dose for the individual patient.

Influence of the administration of amifostine on the pharmacokinetics of 5-fluorouracil in patients with metastatic colorectal carcinoma

A high dose antineoplastic therapy with 5-fluorouracil (5-FU) is associated with severe side effects. It is thought that the cytoprotective drug amifostine can reduce these side effects when it is given prior to a chemotherapeutic course. In this study, the pharmacokinetic parameters of 5-FU are monitored in six patients, who received two chemotherapeutic courses of 2,600 mg/m2 BSA 5FU over 24 h, one course with 700 mg/m2 BSA amifostine prior to the 5-FU infusion and the other without. 20 serum samples were drawn during each infusion time and the 5-FU concentrations were determined by a sensitive and selective GC-MS assay. The statistical analysis of the serum concentrations revealed no significant differences in the pharmacokinetic parameters of 5-FU, whether amifostine is administered or not. The conclusion can be drawn that a reduction of side effects is due to the cytoprotective effect of amifostine and not to a change in the serum concentrations of 5-FU.

Long-term stability of 8-methoxypsoralen in ointments for topical PUVA therapy ('Cream-PUVA')

8-Methoxypsoralen (8-MOP) is an established photochemotherapeutic agent for PUVA therapy. Recently, a so-called 'cream-PUVA' modality was introduced into therapy of psoriasis and other dermatoses. Little is known, however, about the stability of 8-MOP in ointments used for the topical application of this compound. Therefore, we investigated the long-term stability of 8-MOP in three different ointments, Unguentum Cordes(TM), Cold Cream Naturel(TM) and a water-containing gel on the basis of Carbopol 940. All three ointments were prepared with 8-MOP concentrations of 0.05 and 0.005%, and stored over 12 weeks at room temperature (19-20 degrees C) and at 5 degrees C. 8-MOP concentrations were measured at days 1, 8, 15, 29, 57 and 88 after preparation by thin-layer chromatography (TLC). The ointments were dissolved in an organic solvent, 10 microl were transferred onto the TLC plate and the chromatograms were developed first in toluene and then in toluene/ethyl acetate 2:1 v/v to resolve 8-MOP from the ointment constituents. The peak heights of 8-MOP were used for quantitation. The intraday variabilities are <3% for Unguentum Cordes and Cold Cream Naturel and <6% for the Carbopol 940 gel. The interday variabilities were <6.3% in all cases. In Unguentum Cordes and Cold Cream Naturel the concentrations of 8-MOP remain stable, but in Unguentum Cordes the emulsion began to break up after 8 weeks. In the Carbopol gel, only about 40% of the nominal concentrations of 8-MOP were found and they decrease significantly at storage at 5 degrees C. We conclude that the Carbopol gel seems to be unsuitable for PUVA therapy, whereas Cold Cream Naturel shows the best results.

Stability of thiopental and pentobarbital in human plasma determined with a new easy and specific gas chromatography-mass spectrometry assay

A gas chromatographic-mass spectrometric (GC-MS) assay for the determination of thiopental and its main metabolite pentobarbital in human plasma is presented in this study. The sample preparation consists only in the addition of the internal standard barbital and an acidic extraction with ethyl acetate. Analytical separation is accomplished on a RTX-1 15 m x 0.25 mm capillary column with a film thickness of 0.5 micron. The effluent is observed by a mass selective detector operating in the single ion monitoring mode. The limits of detection are 5 ng/ml for pentobarbital and 10 ng/ml for thiopental, the intra-day variabilities are 2.2% and 4.0% and the inter-day variabilities are 3.3% and 7.1% at concentrations of 5 micrograms/ml, respectively. Applying this assay, the stability of thiopental and pentobarbital in human plasma was tested at concentrations of 5 micrograms/ml each. Thiopental is stable in human plasma at least over 41 days stored at -20 degrees C and 5 degrees C, respectively. A decay of about 2%/day is observed under storage at ambient temperature (19-20 degrees C). Pentobarbital is stable under all storage conditions. Methanolic solutions of thiopental are stable for 83 days under storage at 5 degrees C. Aqueous solutions of thiopental-sodium are stable for at least 23 days under storage at 5 degrees C or ambient temperature.

Determination of 1-methylhistamine and 1-methylimidazoleacetic acid in human urine as a tool for the diagnosis of mastocytosis

The determination of the metabolites of histamine, 1-methylhistamine (MHIS) and 1-methylimidazoleacetic acid (MIIA), in human urine is a useful tool for the diagnosis of mastocytosis. MHIS was extracted under basic conditions with chloroform and derivatized with trifluoroacetic acid anhydride, MIIA was derivatized with pentafluorobenzylbromide prior to extraction under basic conditions and the derivative was extracted with chloroform. The samples were assayed by gas chromatography-mass spectrometry. Normal concentrations of MHIS (2.01 micromol l(-1)) and MIIA (21.3 micromol l(-1)) in healthy volunteers' urine samples are clearly detectable with coefficients of variation of 7.0 and 8.9%. Pathological concentrations of 10.1 and 113 micromol l(-1) for MHIS and MIIA, respectively, are quantifiable with coefficients of variation of 6.6 and 4.8%.

Pharmacokinetic data of gamma-linolenic acid in healthy volunteers after the administration of evening primrose oil (Epogam)

Defects in the metabolism of gamma-linolenic acid are thought to play a major role in the pathogenesis of atopic eczema, but little is known about the pharmacokinetic behavior of this fatty acid and its metabolic products. We investigated the serum level-time courses of 8 fatty acids after the administration of Epogam, a preparation of evening primrose oil which contains gamma-linolenic acid as an active ingredient. From 6 volunteers, serum concentration time curves of gamma-linolenic acid and 7 other fatty acids were profiled 24 h with and without the administration of Epogam. Six capsules of Epogam were administered to each subject in the morning at 7:00 and further 6 capsules in the evening at 19:00. On the days of investigation the volunteers had a diet of low fat meals. The serum concentrations of the fatty acids were determined as their methyl esters by means of gas chromatography mass spectrometry. Gamma-linolenic acid shows an absorption-elimination pattern after the administration of Epogam and its AUC24h and Cmax are significantly increased over the baseline values. After the evening administration, t(max) is shorter (2.7 +/- 1.2 h) than after the morning administration (4.4 +/- 1.9 h). The other fatty acids show no significant increase in their concentrations, especially dihomo-gamma-linolenic acid and arachidonic acid, which are metabolic products of gamma-linolenic acid. Conclusively, an effect of the administration of gamma-linolenic acid on the serum concentrations of dihomo-gamma-linolenic acid and arachidonic acid and, therefore, on the biosynthesis of prostaglandin PGE1 and PGE2 could not clearly be established in healthy volunteers. Further investigations will show if there is a significant effect in patients suffering from atopic eczema.