'Wave-type' structure of a synthetic hexaglycosylated decapeptide: a part of the extracellular domain of human glycophorin A.

The three-dimensional structure of a glycopeptide, His-Thr*-Ser*-Thr*-Ser*-Ser*-Ser*-Val-Thr-Lys, with 2-acetamido-2-deoxy-alpha-D-galactose (GalNAc) residues linked to six adjacent amino acids from Thr-10 to Ser-15, was studied by NMR spectroscopy and molecular dynamics (MD) simulations. The hexaglycosylated decapeptide is part of the extracellular domain of human glycophorin A and shows an extended structure of the peptide backbone due to O-glycosylation. Furthermore, each GalNAc residue exhibits one and only one NOE contact from the NHAc proton to the backbone amide proton of the amino acid that the sugar is directly bound to. This indicates a strong preference for the orientation of all GalNAc residues towards the N-terminus. NOE build-up curves were used to determine 42 inter-proton distances that, in connection with phi angles of the peptide backbone obtained from 3J-coupling constants, resulted in constraints for a MD simulation in water. The NMR data and the MD simulations show a preference for an extended backbone structure. The GalNAc residues are located alternatingly on opposite sides of the backbone and reduce the flexibility of the peptide backbone. The conformation of the molecule is relatively rigid and shows a 'wave-type' 3D structure of the peptide backbone within the glycosylation cluster. This new structural element is also supported by the unusual CD spectrum of the glycopeptide.

[Absolute bioavailability of folic acid after oral administration of a folic acid tablet formulation in healthy volunteers]. / Absolute Bioverfügbarkeit von Folsäure nach einmaliger oraler Gabe einer Folsäure-Tablettenzubereitung an gesunde Versuchspersonen.

5 mg folic acid were administered in two sessions to 9 female and 8 male healthy subjects within a balanced 2-way crossover trial either as one Folsan tablet (CAS 59-30-3, test preparation A) or as 2.5 ml of an injection solution (Folsan 2, reference preparation B). Folic acid was determined in serum and urine collected in fractions over 12 h after administration by means of a radioassay. Before each session a saturation period of 9 days duration was performed by administering 1 tablet per day containing 5 mg folic acid followed by a 4-day wash-out period. The mean predose serum level of folic acid amounted to 17.9 +/- 5.62 ng/ml before the oral and 18.2 +/- 5.73 ng/ml before the intravenous administration. The post dose serum levels were corrected with the individual predose levels. After oral administration of test preparation. A a mean peak serum concentration of 243 +/- 33.0 ng/ml (Cmax) was obtained after 2.24 +/- 0.85 h (tmax). The mean area under the corrected serum level time curve was determined with 1160 +/- 177 ng x h/ml (AUC(0-12)). 6 min after intravenous administration serum levels ranged from 559 to 1490 ng/ml. Following correction with the individual predose levels the mean area under the curve amounted to 1550 +/- 249 ng x h/ml. The individual bioavailability ratios of AUC(0-12) (A versus B) varied between 49.3% and 96.7%. The mean absolute bioavailability of folic acid was 76.2% +/- 13.8% (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

[Pharmacokinetics and relative bioavailability of iron and folic acid in healthy volunteers]. / Pharmakokinetik und relative Bioverfügbarkeit von Eisen und Folsäure bei gesunden Versuchspersonen.

The pharmacokinetics and the relative bioavailability of iron and of folic acid was investigated in a randomized, balanced 2-way cross-over study with 14 healthy male participants. The drugs were given in a combined preparation dragée (Ferro-Folsan) containing 100 mg of ferrous-II-sulfate x 1.5 H2O (CAS 13463-43-9) and 0.85 mg of folic acid (CAS 59-30-3). Other established preparations were used as reference drugs. All subjects had a normal iron body level and were brought to a saturated folic acid level prior to the investigation. After administration of 2 dragées of the test medication and determination of serum iron level until 9 h p.a., a relative bioavailability of 64%, compared to an equal dose of a ferrous-II-sulfate-ascorbic acid reference solution, was calculated. From the serum folate AUC (0-9 h) the relative bioavailability was evaluated with 97% for the oral formulation compared to the i.m. administration. The ratio of the cumulative renal folate excretion in the 0-9 h interval amounted to 76% for the oral compared to the i.m. administration. However, in order to understand this differing result it should be kept in mind that during the first hours following parenteral administration a greater amount of the unchanged compound is renally excreted than after oral dosing. This is presumably based upon the different rate of absorption following both administrations with a steeper absorption phase following the parenteral dose.

[Bioavailability of folic acid following intramuscular and intravenous administration to healthy volunteers]. / Bioverfügbarkeit von Folsäure nach intramuskulärer und intervenöser Gabe an gesunde Versuchspersonen.

Bioavailability of Folic Acid Following Intramuscular and Intravenous Administration to Healthy Volunteers 2 mg folic acid (Folsan 2, CAS 59-30-3) were either i.m. or i.v. administered as injection solution to 15 male healthy subjects within an open balanced two-way crossover study. The concentration-time profile of folic acid was determined up to 12 h p.a. in serum and urine using a radioassay. Each change-over phase included a 9 days lasting saturation phase with once-per-day oral administration of a tablet containing 5 mg folic acid. Saturation was performed in order to guarantee filled-up endogenous folate storage compartments in the body of the subjects. After a four-day wash-out phase the subjects were confined and the basic serum level and basic renal 0-12 h folate excretion determined. On the following morning the respective dose of 2 mg folic acid was either i.m. or i.v. applied to the subjects (treatment day 14). 11 (i.m.) and 15 (i.v.) venous blood specimens were drawn up to 12 h p.a. and urine collected following the same schedule as the day before in 4 different fractions. The mean predose level of folic acid in serum was 13.2 +/- 4.85 ng/ml before the i.m. administration and 13.3 +/- 5.59 ng/ml before i.v. administration. The serum concentration data following the respective single administrations were corrected by subtraction of the individual predose values. After 0.50 +/- 0.19 h (mean tmax) the folate serum level increased by 101 +/- 27.2 ng/ml after the i.m. dose. Serum concentration decreased in the following 6-8 h approximately to the predose values.(ABSTRACT TRUNCATED AT 250 WORDS)

Stereoselective high-performance liquid chromatographic determination of flurbiprofen in human plasma.

An enantioselective high-performance liquid chromatographic assay for the quantitation of the enantiomers of flurbiprofen in human plasma is described. The procedure involved extraction of flurbiprofen from acidified plasma into hexane-diethyl ether (8:2, v/v). Stereoselective separation was achieved with a prepacked alpha 1-acid glycoprotein column without any derivatization procedure. A second assay using a conventional reversed-phase column to determine racemic flurbiprofen is also described. The detection wavelength was set at 246 nm. The limit of quantification was found to be 50 ng/ml for both assays. The method was demonstrated to be sufficiently sensitive for stereoselective pharmacokinetic studies of flurbiprofen.

Effect time-course of the inhibition of histamine induced skin reactions by orally applied dimethindene maleate.

We have investigated the time-course of the flare inhibiting activity of dimethindene maleate in man and compared the resulting effect-kinetic data with those from pharmacokinetic investigations. The study was carried out in a double-blind, placebo-controlled cross-over design with randomly assigned healthy volunteers. Dimethindene maleate (4 mg) was orally applied, followed by intracutaneous histamine provocations (-1, 2, 5, 14, 17, 20, 23, 26, 29 h). The two cross-over periods were separated by a wash-out phase of 17 h. Flare areas were documented 5, 10, 20 and 30 min after provocation with histamine. A strong inhibition of the development of flares was observed. With regard to the time-course of the inhibiting effect, its maximum was observed at a provocation time of 5 h. The mean residence time of the inhibiting effect was calculated to be ca. 13 h. This is different from the mean residence time of ca. 8 h obtained from blood level data. Blood- and effect-levels are not linearly related under oral treatment conditions.

Pharmacokinetics of the analgesic o-carbamoylphenoxyacetic acid.

The pharmacokinetics of o-carbamoylphenoxyacetic acid was studied in 9 male healthy subjects following a single i.m. administration of 1000 mg of this compound in form of its sodium salt. Venous blood specimens were drawn up to the 10th h p.a. and the plasma concentration of o-carbamoylphenoxyacetic acid and its metabolite salicylamide were determined using a specific HPLC-assay. Following injection, o-carbamoylphenoxyacetic acid was rapidly distributed in the body since the maximal plasma concentration occurred within 0.37 +/- 0.08 h and was determined with 23.5 +/- 7.51 micrograms/ml in mean. In the following, the plasma concentration declined rapidly as well according to the mean terminal elimination half-life of 0.93 +/- 0.23 h. By contrast, plasma concentration of the metabolite salicylamide was comparatively low. Mean maximal plasma concentration amounted to only 0.18 +/- 0.03 microgram/ml and the peak concentration occurred 1.08 +/- 0.43 h after injection. The mean of the individual areas under the plasma concentration time profiles AUC(O-t) was 30.2 +/- 3.96 micrograms x h/ml for the parent compound and 0.69 +/- 0.14 microgram x h/ml for the metabolite. The relative mass portion of salicylamide vs o-carbamoylphenoxyacetic acid in systemic circulation was estimated with 0.008 comparing mean Cmax and with 0.023 comparing the mean areas AUC(O-t). A possible interpretation of these findings might be that a relatively stable ether bond exists in o-carbamoylphenoxyacetic acid which has to be cleaved during the formation of salicylamide. Due to the moderate rate of metabolic conversion, only minor quantities of salicylamide appeared in the systemic circulation. Furthermore, its peak concentration occurred at a time 2-3 times later than that of the parent compound.

Iron inhibits D-1 dopamine receptor coupled adenylate cyclase via G-proteins in the caudate nucleus of the rat.

The effects of iron ions (Fe(II)sulfate) on basal, forskolin, and dopamine-stimulated activity of adenylate cyclase in membrane preparations from caudate-putamen of the rat have been studied. Iron dose-dependently inhibited both basal and activated adenylate cyclase activity. In contrast to guanylylimidodiphosphate (Gpp(NH)p), guanosine triphosphate (GTP) was found to enhance this inhibitory effect of iron ions. In addition, cholera toxin was able to antagonize the inhibitory effect of iron on forskolin-activated adenylate cyclase. In our preliminary study we suggest an interaction between iron and the guanine nucleotide regulatory subunit. However, further studies are necessary.

The effect of oxiferriscorbone on striatal adenylate cyclase of the rat.

The effects of oxiferriscorbone on basal and forskolin-stimulated activity of adenylate cyclase in membrane preparations from caudate-putamen of the rat have been studied. Oxiferriscorbone, at 30 microM, stimulated the basal activity of the enzyme, but dose-dependently inhibited forskolin-activated activity of adenylate cyclase. Pertussis toxin was found to antagonize this inhibitory effect of oxiferriscorbone. Dopamine stimulated the activity of adenylate cyclase in the striatum, as described previously. When assayed together, the stimulating effects of dopamine and oxiferriscorbone were were additive, implying that they do not act at identical sites. The D1 receptor antagonist, alpha (+)-flupentixol completely blocked the effect of dopamine but had no significant effect on oxiferriscorbone-induced stimulation. The present results suggest that interaction between oxiferriscorbone and the inhibitory guanine nucleotide subunit. However, further studies are necessary.

Pharmacokinetics of S(+)- and R(-)-ibuprofen in volunteers and first clinical experience of S(+)-ibuprofen in rheumatoid arthritis.

S(+)-, R(-)- or racemic ibuprofen was administered orally to volunteers in doses of 150 mg, 300 mg and 500 mg pure S(+)-, 300 mg pure R(-)- and 600 mg racemic ibuprofen. The pharmacokinetic parameters in humans showed that S(+)-ibuprofen was not inverted to R(-)-ibuprofen, whereas R(-)-ibuprofen was inverted to S(+)-ibuprofen to a variable degree. S(+)-ibuprofen and R(-)-ibuprofen given alone more rapidly reached significantly higher maximal plasma concentrations than after the same doses of the racemic compound. The elimination half-lives and clearance values for all three forms of ibuprofen were comparable. The mean residence time of S(+)-ibuprofen after R(-)- and racemic ibuprofen was significantly longer than after administration of the pure S(+)-enantiomer. Judged by the AUC, the bioavailability of S(+)-ibuprofen was independent of the dose within the range tested. Administration of S(+)-ibuprofen to 6 rheumatic patients showed that the pharmacokinetic behaviour of S(+)-ibuprofen in patients was similar to that found in volunteers. S(+)-ibuprofen proved to be an effective analgesic antirheumatic drug in the dose range 1 to 1.5 g/day.

Effect-kinetic characterization of dimethindene maleate following oral administration (Fenistil, Tropfen).

Dimethindene maleate is a well known H1-receptor antagonist with strong affinity to the H1-receptor. In order to evaluate the time course of its activity, dimethindene maleate was investigated in a histamine provocation model in man. Eight healthy male volunteers were treated either with 4 mg dimethindene maleate using a commercially available solution (Fenistile, Tropfen) or an identically appearing placebo solution (po) following a double-blind, crossover study design. Intracutaneous histamine injections were administered at -1, 2, 5, 14, 17, 20, 23, 26 and 29 h following drug administration. Areas of flares and weals were measured 5, 10, 20, and 30 min following histamine provocation. A strong inhibition of the development of flares and weals was observed to be more pronounced in flares than in weals. Baseline adjusted areas under the curve differ statistically significantly following verum and placebo treatment conditions (P = 0.0028). According to the time schedule of the study maximal effects were observed at time point 5 h. The mean residence times of the inhibitory effects were calculated to be congruent to 13 h compared to the mean residence times of dimethindene blood levels of approximately 8 h indicating a non-linear relationship between blood level and effect.

[Effects of low-dose acetylsalicylic acid on thrombocytes in health subjects and in patients with coronary heart disease]. / Wirkungen niedrig dosierter Acetylsalicylsäure auf die Thrombozyten von Gesunden und Patienten mit koronarer Herzkrankheit.

The effects on platelet function of a four-week administration of aspirin at a low dosage (100 mg daily) were compared in two groups, 14 healthy young volunteers and 14 patients with coronary heart disease. In both groups there occurred a clear inhibition of platelet aggregation with collagen (1 and 5 micrograms/l) and arachidonic acid (1 mmol/l) during the aspirin period. The inhibitory effect reached its maximum after three days, remaining at maximum for the remainder of the four weeks. Platelet functions returned to normal within eight days of discontinuing aspirin. The inhibitory effects went together with a definite in-vitro decrease in thromboxane synthesis. In both groups there was no change in aggregation velocity with adenosine diphosphate (ADP) as aggregation-inducing substance, while the frequency of irreversible aggregation decreased with submaximal concentrations of ADP (0.5 and 1.0 mumol/l). The results indicate that low-dose aspirin causes a definite inhibition of platelet function, in a similar manner, in both healthy subjects and patients with coronary heart disease.

High-performance liquid chromatographic determination of ibuprofen, its metabolites and enantiomers in biological fluids.

An isocratic high-performance liquid chromatographic method to determine racemic ibuprofen (assay I) and its major metabolites (assay II) in biological fluids (plasma, urine, bile) using a conventional reversed-phase column is described. A third assay using beta-cyclodextrin as stationary phase (Cyclobond I) for the separation of the ibuprofen enantiomers is also described. A wavelength of 220 nm was used to monitor the substances. The sensitivity of the method was 0.1 microgram/ml for all three assays. The method was demonstrated to be suitable for stereoselective pharmacokinetic studies of ibuprofen in humans and animals.

Pharmacodynamics and pharmacokinetics of furosemide-retard and furosemide-retard/triamterene.

In a randomized cross-over study the saluretic effect of furosemide-retard was compared with the combination of furosemide-retard/triamterene in 10 healthy male volunteers. The combination led to a significantly stronger excretion of sodium and a significantly lower excretion of potassium than furosemide-retard. The interaction of the saluretic with the antikaliuretic was even more distinctly expressed regarding sodium related quotients. The combination furosemide-retard/triamterene differs significantly from furosemide-retard in the main considering Na+/Cl-, Na+/K+ and Na+/Mg2+ quotients. The concentration time curves for furosemide and OH-TA-sulphate in the plasma are nearly similar. Maximal plasma levels for furosemide are reached after 3.9h and for OH-TA-sulphate after 2.2h. The 'apparent' elimination half-life time for furosemide is 2.1h and the elimination half-life time for OH-TA-sulphate is 2.0h.

[Distribution of 4-14C-mofebutazone in the rat]. / Zur Verteilung von 4-14C-Mofebutazon bei der Ratte.

To further elucidate the distribution and differentiation of mofebutazone in comparison to phenylbutazone, 6 rats received 200 mg/kg 4-14C-mofebutazone corresponding to approx. 27 microCi/animal. 2 animals were sacrificed each time after 45 min, 6 h and 24 h. The 4-14C-plasma level was determined at the corresponding test periods and the radioactivity eliminated within 24 h in the urine was also determined. In addition autoradiograms of the whole animal were prepared for each animal. According to this study 4-14C-mofebutazone is distributed mainly in the metabolisation and elimination organs, a moderate activity was to be found under the skin and muscle tissue, but none, however, in the central nervous system and the bone marrow. Nearly 81% of the substance was eliminated after 24 h and with exception the colon the corresponding autoradiograms were practically free of activity. Because of the short half-life time and the rapid elimination mofebutazone does not lead to any accumulation.

Dose-dependent pharmacokinetics of dexamethasone.

The dose dependency of the pharmacokinetics of dexamethasone and its influence on the endogenous secretion of cortisol has been studied in healthy females. The maximum plasma level occurred between 1.6 and 2.0 h after doses of 0.5-3.0 mg independent of the type of administration. AUC, distribution volume, plasma clearance and cmax did not increase in proportion to the dose but only by the factor of about 0.6-0.7 after the oral administration of 0.5-1.5 mg. Comparatively high values were reached after 3.0 mg i.m. This may be due to reduced bioavailability of the oral doses. Within the first 12 h after the administration of 0.5-3.0 mg, endogenous cortisol secretion was influenced independent of dose. However, the suppressive effect after 24 h was dose dependent and amounted to approximately 24% for 0.5 mg p.o., 62% for 1.5 mg p.o. and 90% for 3.0 mg i.m. In the case of administration every second day, the integral reduction within 24 h after the administration of 0.5 mg dexamethasone was 44 to 65% and for 1.5 mg between 59 and 62%.

[Pharmacology, toxicology and pharmacokinetics of mofebutazone]. / Zur Pharmakologie, Toxikologie und Pharmakokinetik von Mofebutazon.

The difference between mofebutazone and phenylbutazone is shown by means of toxicological, pharmacological and pharmacokinetic studies as well as by the protein binding. In spite of a certain chemical similarity both substances differ distinctly. Mofebutazone is approx. 5-6 times less toxic than phenylbutazone but its analgesic and antiphlogistic effects are weaker than those of phenylbutazone. The half life time of mofebutazone of 1.9 h is considerably shorter than that of phenylbutazone (54-99 h). Mofebutazone, in contrast to phenylbutazone, is mainly glucuronidised and to 94% eliminated within 24 h, phenylbutazone on the other hand to only 88% within 21 days. In spite of a high plasma protein binding quota of 99%, mofebutazone is classed among those substances with a medium binding potential. Conclusions may only be drawn with great reservation with regard to a category of substances from the effect and side effects of one substance on the basis of the present studies.