Absorption, distribution, metabolism and excretion of cizolirtine, a new analgesic compound, in rat and dog.

1. The pharmacokinetics of cizolirtine citrate, a new analgesic compound, were studied in the rat and dog following single oral and intravenous doses. 2. Absorption of radioactivity was fast and complete regardless of the species, and no dose and food-related differences were found. However, the elimination half-life of unchanged cizolirtine was shorter in rat than in dog. 3. Tissue distribution of total radioactivity in rat differed widely and a high affinity for liver, kidney, gastrointestinal and pigmented tissues was observed. In blood and almost all tissues the highest concentrations were reached at 20 min; beyond that time the decline of radioactivity in most tissues was parallel to that in blood. 4. The percentage of radioactivity excreted in the rat was 68% in urine and 21% in faeces, the latter being apparently due to drug enterohepatic circulation. In the dog, 92 and 4% of the radioactivity was found in urine and faeces respectively. The contribution of renal excretion to cizolirtine elimination was <5% in rat and 20% in dog. Twelve metabolites were detected in rat and six in the dog by radio-hplc analysis of urine.

Absorption, distribution and excretion of [14C]E-4716 after single-dose administration in rats and dogs.

The absorption, distribution and excretion of E-4716, a novel antihistamine, were studied in rats and dogs after single-dose oral or intravenous administration of [14C]E-4716. Radioactivity was rapidly and efficiently absorbed from the gastrointesanal tract after oral administration, and biphasic plasma concentration-time profiles were observed in both species. In rats, oral absorption was linear within the dose range studied, and no differences in administration route or doses were observed in elimination. Elimination was approximately twice as fast in dogs as in rats. No sex differences in elimination were observed in dogs. Radioactivity was widely distributed in rats, and levels in brain, eyes, fat and testes were lower than those in plasma. Excretion was mainly by feces in rats and by urine in dogs, showing species differences. After oral administration in rats, unchanged drug was rapidly absorbed and the absolute bioavailability was only 20%, suggesting an important first-pass effect.

Absorption, distribution and excretion of [14C]-Lesopitron after single and repeated administration in rats and dogs.

Disposition of [14C]-lesopitron was investigated in male rats and dogs after single and repeated oral administration. Radioactivity was rapidly and efficiently absorbed from gastrointestinal tract following oral administration. After 7 days, the radioactivity was mainly excreted into feces via bile. The cumulative urinary and fecal excretion was 99% and 75% of the administered dose in rats and dogs, respectively. [14C]-Lesopitron was widely distributed in rats, with the highest concentrations in liver and kidney, while the concentration in brain was similar to that in plasma. Radioactivity in most tissues decreased essentially in parallel with that in plasma. In rats, plasma levels of [14C]-lesopitron radioactivity achieved steady state on day 2 of repeated administration. The distribution pattern obtained after 7 consecutive daily oral doses was similar to that in the single-dose study. At 72 h after the last administration, tissue radioactivity was fully eliminated and no accumulation occurred. After i.v. administration in rats and dogs, plasma concentrations of lesopitron decreased biphasically with an apparent elimination half-life of 100 min. The absolute bioavailability of lesopitron was about 10%, suggesting an important first-pass effect. In rats, the lesopitron plasma concentrations were similar to those obtained for its metabolites (5-hydroxylesopitron and PmP), whereas in dogs, the PmP plasma concentrations were higher than those for lesopitron and 5-hydroxylesopitron.

Anatomy of segmental duplication in the human basilar artery. Possible site of aneurysm formation.

Segmental duplications of the basilar artery, previously reported exclusively as anatomical variations, owe their clinical interest to the possible association with aneurysms localized at the junctions of the fenestrated segments. The morphological characteristics of 5 cases of basilar artery segmental duplication without aneurysms, found at autopsy, are reported. In 3 of these the proximal junction of the fenestrated segment was studied with scanning electron microscopy and morphometry. In all cases the tunica media of the medial wall of the 2 branches showed a progressive thinning towards the junctions of the fenestrated segments and a small muscular gap at their apex. The limited medial defect might be embryologically ascribed to the persistence of the morphological individuality of the tunica media of the 2 branches at the point where the fusion of the primitive longitudinal neural arteries stopped. The review of the literature shows that the morphology of the junctions of the fenestrated segments is in conformity with that of the intracranial arterial bifurcations. For this reason the basilar artery fenestration exposes to the blood flow a new distal bifurcation where the same etiologic factors that are still under discussion in the origin of saccular intracranial aneurysms may be active.

Automated high-performance liquid chromatographic assay for lesopitron, a novel anxiolytic, in human plasma using on-line solid-phase extraction.

A totally automated liquid chromatographic assay method based on a Prospekt solid-phase extraction unit was developed for the analysis of lesopitron and its metabolite 5-hydroxylesopitron in human plasma. On-line solid-phase extraction of lesopitron, 5-hydroxylesopitron and its internal standard in human plasma was carried out using C2 cartridges. After washing, the test substances were eluted with mobile phase onto an ODS-2 Inertsil column and measured by fluorescence detection. The total time for one analysis was 25 min. The method developed was selective and linear in the concentration range from 1 to 40 ng/ml for both parent drug and metabolite. Recovery of lesopitron and 5-hydroxylesopitron were higher than 80% and the quantification limits were 1 ng/ml for both compounds. Coefficients of variation obtained for precision parameters were all below 14.5% and 13.9% for parent drug and metabolite, respectively. Good values of accuracy were also obtained.

Cu(II) and Cd(II) inhibition of rat liver glutathione S-transferase. A steady-state kinetic study.

The true Michaelis constant for GSH and CDNB was 0.287 mM and 0.180 mM, respectively. Regarding the quantitative effect of Cu(II) and Cd(II) inhibition on the GST system, the I50 value for Cu(II) was 0.250 mM; in contrast, Cd(II) GST-inhibition did not reach the I50 value. When the varied substrate was GSH and CDNB was fixed at saturant concentration, the Cu(II)-inhibition was consistent with a pure competitive pattern. However a mixed pattern was found when CDNB was the varied substrate and GSSH was fixed at saturant concentration. The Cd(II) inhibition effect was consistent with an uncompetitive pattern when GSH was the varied substrate and CDNB was kept at saturant level. When CDNB changed over an extensive range of concentration, the inhibition effect shows a mixed inhibition pattern with a competitive character. In addition the inhibition constants of Cu(II) were one order of magnitude lower than those of Cd(II).

Glutathione and related enzyme activity in the 11-day rat embryo, placenta and perinatal rat liver.

Glutathione reductase (EC 1.6.4.2; GSSG-R), glutathione peroxidase (EC.1.11.1.9; GSHpx) and glutathione transferase (EC 2.5.1.18; GST) enzymatic activities and glutathione status were investigated in 11-day embryos and the yolk sac, placenta and perinatal liver in rats. It is observed that: (a) levels of GSSG differ between the embryo (lower) and yolk sac (higher); (b) GSH concentrations increased significantly in fetal livers with respect to the days of gestation; in contrast, GSSG hepatic concentrations showed a significant rise with respect to time only during lactation; (c) the specific enzymatic activity of both GSHpx and GSSG-R were higher in the visceral yolk sac than in the embryo; (d) hepatic GSSG-R activity increased significantly during gestation. In addition, hepatic GSHpx and GST activities showed statistically significant increases over the period studied.

Steady-state kinetic studies of glutathione reductase.

The steady-state kinetic studies of yeast glutathione reductase, performed when [GSSG] = 10[NADPH] in the assay mixture, show that at concentrations of GSSG under 450 microM the enzymatic mechanism pathway is ping-pong. Furthermore, in the case of higher values, the enzymatic kinetics follows a sequential pathway. However when the glutathione reductase reaction passes to the ping-pong mechanism, the inhibition effect by excess of NADPH is stronger than when the reaction takes place over the sequential mechanism.

Zn(II), Cd(II) and Cu(II) interactions on glutathione reductase and glucose-6-phosphate dehydrogenase.

Kinetic characterization of the inhibition effects of Cd(II), Cu(II) and Zn(II) on glutathione reductase (GSSGR; EC 1.6.4.2.) and glucose-6-phosphate dehydrogenase (G6PD; EC 1.1.1.49) from Saccharomyces cerevisiae was made. No inhibition effect was found with Zn(II) on these enzymatic systems. The effect of Cd(II) (up to 0.16 mM) and Cu(II) (up to 0.008 mM) on GSSGR activity is consistent with a pure competitive inhibition or an uncompetitive pattern, when the varied substrate is the oxidized glutathione or the NADPH, respectively. Only Cd(II) (up to 1.0 mM) showed an inhibition effect on G6PD system, which is consistent with a mixed-type inhibition pattern. When NADP+ changes over an extensive range of concentration, the inhibition effect shows an uncompetitive character. Furthermore, when G-6-P is the varied substrate, the character of the mixed-type inhibition is competitive.

A micromethod for the enzymatic estimation of the degree of glycogen ramification.

A comparison of methods for the evaluation of glycogen content in liver tissue of rats has been carried out by determining the recoveries in the differential ethanol precipitation of glycogen from alkaline tissue digests as well as the actual quantitative equivalence between glycogen content and actual glucose measured. Hydrolytic/enzymatic methods gave lower results than non-specific chemical methods such as anthrone. These lower values, combined with the losses in the purification process resulted in much lower glycogen estimations than the actual estimated tissue content. A method has been devised for the measurement of glycogen ramification in small liver tissue samples, using neutral periodate oxidation of the molecule, followed by determination of the formic acid evolved from the branch ends with formic acid dehydrogenase. The method gave results very similar to the classical methods in which the acid formed is measured titrimetrically. Rat liver tissue contained a mean 323 +/- 69 mmol of glucose equivalents of glycogen per gram of tissue; this glycogen had a mean chain length of 11.4 +/- 0.8 units.