Gentamicin-induced stimulation of DNA synthesis in rat kidney. Comparison between in vivo and in vitro models

We have performed combined in vivo and in vitro measurements of thymidine uptake into kidney cortex DNA of animals treated with gentamicin for 7 days at 10 or 20 mg/kg daily (BID). Labelled thymidine is taken up by cortex fragments in vitro (90 min incubation) and incorporated into DNA; treatment of the animals with gentamicin results in a significant dose-dependent enhancement of this in vitro thymidine incorporation; labelled cells are found primarily in the proximal tubules and interstitium; there is an excellent correlation (r : 0.983, n = 15) between the changes of incorporation measured in vivo and in vitro as demonstrated by the sequential use of [3H]thymidine (in vivo) and [14C]thymidine (in vitro) within the same animals.     

Inhibition of histamine synthesis in vitro and in vivo by S-alpha-fluoromethylhistidine

(S)-alpha-Fluoromethylhistidine (alpha-FMH) is a Kcat or "suicide-substrate" inhibitor of partially purified mammalian histidine decarboxylase; i.e. the agent is converted enzymatically to a more active form which effects a time-dependent, irreversible inhibition. Incubation of a alpha-FMH[4-3H] with enzyme and pyridoxal phosphate resulted in an apparently irreversible labeling of protein, with no demonstratable formation of free-amine product, suggesting a very low to non-existent turnover ratio. alpha-FMH was accumulated in isolated mastocytoma cells and effected a time-dependent inhibition of the conversion histidine[3H]----histamine[3H], the latter product having a markedly different distribution between cells and medium than the pre-existing histamine pool. Inhibition of whole-body histidine decarboxylase activity, as specifically measured by alpha-methylhistidine-14COOH----14CO2, was also time dependent. Concomitant reduction in histamine levels was seen only in the rapidly turning-over pools of stomach and brain. However, over the course of 13 weeks of chronic treatment, depletion of the relatively inert mast-cell histamine pool(s) was seen as well.     

PEG-metronidazole conjugates: synthesis, in vitro and in vivo properties

Metronidazole (MTZ), a drug used for the treatment of protozoal infections caused by protozoa and anaerobic microorganisms, was conjugated to linear or branched poly(ethylene glycol) of 5,000, 10,000 and 20,000 Da. An ester linkage between polymer and drug was used in the coupling to yield a polymeric prodrug. The modification allowed overcoming the known MTZ solubility problem leading us to obtain a bioconjugate more suitable for parental administration. The conjugates of various molecular weight polymers have been tested in vitro toward chemical degradation and digestive enzymes. It was found that molecular weight and shape of PEG is critical for the prodrugs stability. Good resistance in the stomach acidic media was found and a slow release of the drug in the large intestinal fluid may take place. In vivo studies carried out following i.v. or s.c. administration to mice revealed improved pharmacokinetics properties upon conjugation.     

Ketorolac-dextran conjugates: synthesis, in vitro and in vivo evaluation

Ketorolac is a non-steroidal anti-inflammatory drug. Dextran conjugates of ketorolac (KD) were synthesized and characterized to improve ketorolac aqueous solubility and reduce gastrointestinal side effects. An N-acylimidazole derivative of ketorolac (KAI) was condensed with a model carrier polymer, dextran of different molecular masses (40000, 60000, 110000 and 200000). IR spectral data confirmed formation of ester bonding. Ketorolac contents were evaluated by UV-spectrophotometric analysis. The molecular mass was determined by measuring viscosity using the Mark-Howink-Sakurada equation. In vitro hydrolysis studies were performed in aqueous buffers (pH 1.2, 7.4, 9) and in 80% (V/V) human plasma (pH 7.4). At pH 9, a higher rate of ketorolac release from KD was observed as compared to aqueous buffer of pH 7.4 and 80% human plasma (pH 7.4), following first-order kinetics. In vivo biological screening in mice and rats indicated that conjugates retained analgesic and anti-inflammatory activities with significantly reduced ulcerogenicity compared to the parent drug.     

Suppression of aminoacyladenylate synthesis by methyl mercury in vitro and in vivo

Methyl mercury (MeHg) at a concentration of 20 microM significantly inhibits the synthesis of aminoacyladenylates (AAA) in vitro from serine and histidine, and fails to inhibit AAA synthesis from phenylalanine, leucine, arginine and aspartate. In vivo administration of MeHg (single i.p. injection of 50 nmol/g body weight) leads to 75-80% suppression of AAA synthesis from serine, histidine, phenylalanine, leucine, arginine and aspartate in rat brain tissue.     

Homologous oxypiperidines as inhibitors of protein synthesis in vitro and ex vivo

The antioxidant nitroxyl-2 (2,2,6,6-tetramethyl-4-oxypiperidine-1-oxyl) is an active inhibitor of protein synthesis both in vitro (rabbit reticulocyte lysate cell-free translation system) and ex vivo (mouse liver). Demethylated derivatives of this agent demonstrate a significantly lower inhibitory activity. There is a strong positive correlation between quantitative parameters of toxicity, the ex vivo and in vitro inhibitory effects on translation, and the total number of methyl groups per drug molecule.     

Effect of sparsomycin in vivo and in vitro on hepatic polyribosomes and protein synthesis

Sparsomycin (20 μg/20 g of body wt), when administered intraperitoneally to mice, induced marked disaggregation of hepatic polyribosomes and inhibited incorporation of [¹⁴C]leucine into hepatic proteins by 90 per cent. However, addition of Sparsomycin in vitro to a cell-free amino acid incorporating system did not cause disaggregation of polyribosomes, yet inhibited the incorporation of [¹⁴C]leucine into proteins by 80 per cent. In studies concerned with initiation of protein synthesis, it was observed that Sparsomycin inhibited the factor-dependent initiation of new polyphenylalanine chains, as well as factor-dependent binding of either phe-tRNA or met-tRNA to 40S ribosomal subunits. These findings are interpreted as suggesting that, in vivo, Sparsomycin disaggregates polyribosomes probably by interfering with the initiation process.     

Antitracheobronchospastic interaction in vitro and in vivo between salbutamol and flunisolide

Salbutamol and flunisolide, when administered in association, are able to potentiate their effects both in vitro and in vivo on relaxation of the tracheobronchial smooth muscle of the guinea-pig.     

盐酸噻吩诺啡缓释微球的体外释放度及其体内外相关性研究

目的 建立体内外相关性良好的盐酸噻吩诺啡缓释微球的体外释放度测定方法.方法 采用直接释药法和透析释药法测定盐酸嚷吩诺啡缓释微球的体外释放度;采用高效液相色谱法测定盐酸噻吩诺啡缓释微球在大鼠注射部位的残留量,计算微球在体内的释药速度.通过相关性评价确定最佳的体外释放度测定方法.结果 透析释药法和直接释药法均可获得良好的体内外相关性.结论 直接释药法和透析释药法均可用于测定盐酸噻吩诺啡微球的体外释放度.     

重组人红细胞生成素体内外活性检测方法的比较

目的对重组人红细胞生成素 (rhEPO)体内外活性测定结果进行比较 ,说明体内外活性测定对rhEPO质量控制的意义。方法采用59Fe摄入法、网织红细胞法和ELISA法测定rhEPO制品的体内外生物学活性。结果59Fe摄入法和网织红细胞法测定结果一致 ,与rhEPO唾液酸含量具有相关性。当rhEPO唾液酸含量较低时 ,ELISA法与体内活性测定结果有较大差异。结论rhEPO体内外活性测定方法可以相互补充 ,均是保证rhEPO质量不可缺少的质控手段。     

卡马西平片体外溶出度与体内吸收相关性

目的：考察卡马西平（ＣＢＺ）片溶出度与体内吸收的相关性。方法：应用ＺＲＳ－４溶出度仪测定卡马西平片的溶出度。４名男性健康志愿性ｐｏ单剂量２００ｍｇＣＢＺ用ＴＤｘ分析仪测定血药浓度，并按照Ｗａｇｎｅｒ－Ｎｅｌｓｏｎ公式计算药物吸收分数。结果：体外溶出度与体内药物吸收分数的相关系数ｒ＝０．９２６１，体外溶出度与体内药物吸收分数的相关系数ｒ＝０．９９７７。结论：ＣＢＺ片体外溶出度与体内吸收有较好的相关性     

Interaction between mesna and selected transition metals in vitro and in vivo

The interactions between mercaptoethanesulphonic acid (mesna) and transition metal ions was investigated. Mesna was shown to react with selected transition metals (to form covalent metal thiol compounds) resulting in reduction of their oxidation state with the possible concomitant oxidation of mesna to dimesna. The reactions between mesna and copper were investigated in detail. Mesna is known to bind to serum albumin, copper was found to chemically combine with the mesna protein complex. Administration of copper to rats resulted in accumulation of copper in the kidney, while simultaneous administration of mesna and copper resulted in accumulation of copper in liver. The possible role of mesna-albumin complexes in copper transport is postulated and the importance of this in cancer treatment, where serum copper levels are often raised, is discussed.     

Interactions between ultrafine particles and transition metals in vivo and in vitro

The present study investigates whether 1-->3-beta-glucans (zymosan particles) modify the pulmonary response of rats to endotoxin (lipopolysaccharide, LPS). Initial experiments were conducted to establish appropriate doses of LPS and regimens for exposure to zymosan and LPS. Interaction between zymosan and LPS exposures was determined to be the deviation from the sum of the individual effects of these agents. Treatment with zymosan on Day 1 and LPS on Day 2 modified several indices of pulmonary responsiveness, including tumor necrosis factor-alpha, albumin, and lactate dehydrogenase activity (LDH) in first acellular lavage fluid as well as the levels of chemiluminescence (CL), NO-dependent CL, and nitric oxide production in cultured lavaged alveolar macrophage cells determined 1 day after exposure. No significant deviation from additivity was found for breathing rate increase and polymorphonuclear leukocytes infiltration. Simultaneous administration of zymosan and LPS or administration of LPS before zymosan did not change these indices of pulmonary responsiveness. These data suggest that the inhibitory effect of 1-->3-beta-glucans on pulmonary responsiveness to endotoxin exposure was apparent only when rats were pretreated with 1-->3-beta-glucan. These results suggest that complex interaction of components may exist in exposure to organic dusts. Therefore, hazard may not be defined by measuring endotoxin or 1-->3-beta-glucans alone.