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  • 1
    Electronic Resource
    Electronic Resource
    The disposition of 3H-(−)noradrenaline in the Perfused cat and rabbit heart (1981)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 318 (1981), S. 71-82 
    Details
    ISSN: 1432-1912
    Keywords: (−)Noradrenaline ; Neuronal metabolism ; Extraneuronal metabolism ; Perfused heart ; Efflux of noradrenaline metabolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Hearts of cats and rabbits were perfused at a constant rate with 3H-(−)noradrenaline for 60–120 min. During the perfusion the rate of net removal of 3H-noradrenaline from the perfusion fluid and the rate of efflux of 3H-metabolites from the hearts were followed. From these results and from the amount of 3H-metabolites recovered from the hearts (at the end of experiments), the time course of the cumulative metabolite formation was obtained. The following metabolites were determined: 3,4-dihydroxyphenylethyleneglycol (DOPEG), 3,4-dihydroxymandelic acid (DOMA), normetanephrine (NMN) and a fraction consisting of 3-methoxy-4-hydroxyphenylethyleneglycol and 3-methoxy-4-hydroxymandelic acid (OMDA). 2. In normal hearts, the rate of formation of DOPEG, DOMA and OMDA became constant only after a considerable delay, and the rate of efflux of these metabolites did not reach a constant value within 120 min. By contrast, the formation of NMN proceeded at a constant rate throughout the perfusion with 3H-noradrenaline, and the rate of efflux of NMN approached a steady level within about 30 min. 3. In hearts of reserpine-pretreated animals not only NMN, but also DOPEG, DOMA and OMDA quickly approached a constant rate of formation. In addition, the efflux of all metabolites attained a steady level, and after about 70 min, the hearts of both species reached a steady state in which the net removal of 3H-noradrenaline was fully accounted for by the formation of metabolites. 4. The metabolite pattern during the steady state showed striking species differences. The rate of metabolite formation (expressed in % of the steady-state rate of 3H-noradrenaline removal) decreased in the order DOPEG (40.0%)〉NMN (30.8%)〉DOMA (18.1%)〉OMDA (9.0%) in the cat heart and DOPEG (66.8%)〉DOMA (20.0%)〉OMDA (6.6%)〉NMN (1.5%) in the rabbit. 5. In both species, 30 μmol · l−1 cocaine (to inhibit neuronal uptake) decreased the rate of formation of DOPEG, DOMA and OMDA to very low values, but increased the formation of 3H-NMN. 6. In the cat heart, 30 μmol · l−1 hydrocortisone (to inhibit extraneuronal uptake) decreased the formation of NMN, while having no effect on the formation of DOPEG, DOMA and OMDA. Moreover, in the cat and rabbit heart perfused in the presence of cocaine, inhibition of extraneuronal uptake markedly affected the formation of NMN. 7. A linear relationship was found for all metabolites between the rate of efflux and the tissue content (both parameters being determined during steady state), indicating first-order kinetics of efflux. The ranking order of the overall rate constants for efflux was DOPEG≫NMN〉DOMA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00508829
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  • 2
    Electronic Resource
    Electronic Resource
    Tetrodotoxin-sensitive and-resistant effects of veratridine on the noradrenergic neurone of the rat vas deferens (1983)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 324 (1983), S. 264-270 
    Details
    ISSN: 1432-1912
    Keywords: Veratridine ; Exocytotic release ; Neuronal efflux ; “Reserpine-like” effects ; Rat vas deferens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1) The veratridine-induced release of 3H-noradrenaline from noradrenergic neurones was examined in the isolated vas deferens of either untreated or reserpine plus pargyline-pretreated rats. The rat vas deferens, whose catechol O-methyltransferase was inhibited, was first incubated with 0.4 μmol/l 3H-(−)noradrenaline (30 min) and then washed repeatedly with amine-free solution. After 120 min (i.e., well after the efflux of tritium from the tissue had reached a steady level and was predominantly of neuronal origin), washout was continued in the presence of veratridine for further 10–15 min. 2) In vasa deferentia of untreated rats, variatridine (1–100 μmol/l) caused a concentration-dependent increase in the efflux of tritium. At high concentrations of the drug (30 or 100 μmol/l), this increase in efflux was peak-like during the first 3 min (“peak response”) and then fell to a plateau (“plateau response”). In the presence of veratridine, unchanged 3H-noradrenaline accounted for about 75% of the tritium efflux (the rest being represented by deaminated 3H-catechol metabolites). 3) The “peak response” to veratridine (100 μmol/l) was abolished by tetrodotoxin (TTX; 1 μmol/l) or the absence of external Ca2+. Cocaine (10 μmol/l) affected neither the “peak response” as such nor the contribution by 3H-noradrenaline to the efflux of tritium during that response. Hence, the “peak response” was due to exocytotic release of 3H-noradrenaline from the neurone. 4) The “plateau response” to veratridine (100 μmol/l) was unaffected by the absence of external Ca2+, largely resistant to TTX (1 μmol/l) and moderately reduced by cocaine. However, both TTX and cocaine drastically changed the composition of the radioactivity during the “plateau response”: they greatly reduced or even abolished the efflux of unchanged 3H-noradrenaline and markedly increased the efflux of deaminated 3H-metabolites. Hence, the “plateau response” represented a “reserpine-like” vesicular effect of varatridine; the ensuing 3H-noradrenaline efflux out of the neurone was mediated by the neuronal amine carrier. 5) After pretreatment with reserpine (to inhibit vesicular uptake) and pargyline (to inhibit monoamine oxidase), veratridine (100 μmol/l) elicited a phasic, peak-like increase in the efflux of tritium (about 90% of which was unchanged 3H-noradrenaline). This response to veratridine was abolished by TTX (1 μmol/l) and unaffected by the absence of external Ca2+; moreover, it was greatly reduced by either cocaine (10 μmol/l) or desipramine (1 μmol/l) and, hence brought about by carrier-mediated outward transport across the axonal membrane. 6) It is concluded that, in addition to its well-known action on the fast sodium channel, veratridine somehow increases the leakage of noradrenaline from storage vesicles; this “reserpine-like” effect of veratridine is resistant to TTX and therefore not a consequence of the drug-induced changes in the sodium permeability of the axolemma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00502621
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  • 3
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of ciprofloxacin after oral and intravenous administration in healthy volunteers (1984)
    Springer
    European journal of clinical microbiology & infectious diseases 3 (1984), S. 355-359 
    Details
    ISSN: 1435-4373
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The pharmacokinetics of ciprofloxacin (Bay o 9867) was examined after a single oral dose of 250 mg and a single intravenous dose of 100 mg respectively in six healthy male volunteers in an open, randomized crossover study. Although ciprofloxacin concentrations were measured in serum, plasma and urine by HPLC with fluorimetric detection and by microbiological assay, all pharmacokinetic calculations are based on the highly sensitive HPLC method only. The mean serum concentration of ciprofloxacin peaked approximately1 h after the oral dose (0.94 mg/l). The elimination half-life was about 4 h and the renal clearance was 4.75 ml/min·kg; both were independent of the route of administration. The total clearance (9.62 ml/min·kg) was about twofold higher than the renal clearance. The volume of distribution of the central compartment was calculated to be 0.16 l/kg and the total volume at steady state was 2.0 l/kg. About 27 % of the oral dose was excreted in urine, whereas the urinary recovery of the i.v. dose was 46 %. The absolute bioavailability of ciprofloxacin was found to be approximately 60 %. Ciprofloxacin appears to follow first-order, three compartment model kinetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01977494
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    Paper (German National Licenses)
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