人参总皂甙对14C-花生四烯酸在兔血小板中代谢的影响

本文报道人参总皂甙对花生四烯酸在免血小板中代谢的影响。方法采用放射薄层扫描、放射自显影及放射活性测定等同位素技术。结果表明,人参总皂甙抑制兔血小板血栓素A₂的生物合成,并呈量效关系。同时对前列腺素A₂也有抑制作用。这种抑制怍用的机理,可能是人参总皂甙抑制了血小板环氧酶和血栓素A₂合成酶的活性。     

CCl4致大鼠慢性肝损伤模型参数优化及代谢组学评价

目的 研究CCl₄致大鼠慢性肝损伤模型的最佳造模剂量和时间,并进行代谢组学评价。方法 SPF级雄性SD大鼠随机分为6组,即对照组和10%、20%、30%、40%、50% CCl₄组。CCl₄组sc给予不同浓度的CCl₄大豆油溶液,注射体积为2 mL/kg,每周2次,连续8周,对照组给予等体积溶剂油。大鼠于造模0、2、4、6、8周末置代谢笼12 h收集尿液,取出后采用眼球后静脉丛穿刺法取静脉血0.3 mL,常规分离血清;4、6周末各处死3只大鼠,取肝脏;8周末造模后处死大鼠,分离各脏器,称质量计算脏器系数。观察动物体质量、肝脏外观和病理切片、全自动生化仪检测血清丙氨酸转氨酶（ALT）和天门冬氨酸转氨酶（AST）。对10% CCl₄组尿液进行氢核磁共振（¹H-NMR）代谢组学测定,运用SPSS、MatLab7.5、SIMCA-P软件对数据进行分析。结果 对照组大鼠体质量保持增长;随着CCl₄剂量增高,各模型组大鼠体质量增长速度渐趋缓慢。造模8周后,与对照组比较,10% CCl₄组肝脏系数显著升高（P<0.01）,其他组肝脏系数无显著性变化;20%~50% CCl₄组的脾脏、肾脏系数,20%、40%、50% CCl₄组的肺脏系数均显著升高（P<0.05、0.01）。造模4周后,10% CCl₄组大鼠肝脏出现了慢性炎症表现,而20%~50% CCl₄组大鼠肝脏损伤明显,出现明显坏死现象;6周后,造模组大鼠肝脏均出现肝硬化病变。造模组大鼠血清ALT和AST与对照组比较均显著升高（P<0.05、0.01）,且均出现了先升高后降低趋势。代谢组学研究结果显示,造模4周起大鼠尿液与0周可以显著分离。共寻找到差异代谢物15个,6条重要的代谢通路,涉及能量代谢、脂质代谢、氨基酸和核苷酸代谢等途径。结论 慢性肝损伤模型造模剂量以10% CCl₄、2 mL/kg为宜,造模时间以4~6周为宜,代谢组学研究可以动态追踪造模过程。     

89SrCl2治疗恶性肿瘤骨转移的影响因素分析

目的 探讨⁸⁹SrCl₂治疗恶性肿瘤骨转移的疗效影响因素。方法 选择南充市川北医学院附属医院2013年2月至2016年9月行⁸⁹SrCl₂治疗的恶性肿瘤骨转移患者99例,分析患者的年龄、性别、肿瘤病理类型、⁸⁹SrCl₂治疗次数、手术切除原发灶、放疗、化疗、肿瘤骨转移的病灶数量、联合止痛药状况以及碱性磷酸酶（ALP）是否会影响⁸⁹SrCl₂的治疗效果。结果 ⁸⁹SrCl₂治疗的总有效率为63.6%。单因素分析结果显示不同肿瘤病理类型、不同治疗次数、是否联合放射治疗、是否手术切除原发灶、不同肿瘤骨转移病灶数量及是否联合止痛药患者的治疗效果进行比较,差异具有统计学意义（P<0.05）。logistics回归分析显示,患者的肿瘤病理类型、⁸⁹SrCl₂治疗次数、手术切除原发灶、肿瘤骨转移的病灶数量及联合止痛药是影响⁸⁹SrCl₂疗效的独立因素（P<0.05）。结论 肿瘤病理类型、⁸⁹SrCl₂治疗次数、手术切除原发灶、肿瘤骨转移病灶数量以及联合止痛药能影响⁸⁹SrCl₂治疗恶性肿瘤骨转移的疗效。     

神经肽DGAVP和Org2766对神经细胞内游离Ca2+的影响

运用Ca²⁺指示剂Fura-2作为细胞内钙离子的荧光探针,利用AR—CM—MIC阳离子测定系统,检测了分离的神经细胞内游离钙及其变化,并观测了DGAVP和Org2766对蛋白质合成抑制剂茴香霉素(ANI)引起细胞内钙离子浓度([Ca²⁺]_i)变化的影响。结果表明茴香霉素可使[Ca²⁺]_i显著升高,且有量效关系;DGAVP本身并不引起[Ca²⁺]_i发生显著变化,但适当剂量的DGAVP可显著对抗一定剂量范围内ANI升高[Ca²⁺]_i的作用,提示DGAVP对抗ANI的蛋白质合成抑制效应可能是通过拮抗ANI升高[Ca²⁺]_i这一途径实现的,另一神经肽Org2766则可能不是通过这一机制发生作用。从细胞内Ca²⁺的角度看,这两种肽的作用机理显然是不同的。     

银杏叶提取物对低氧复氧、H2O2和谷氨酸损伤时谷氨酸引起的大鼠星形胶质细胞［Ca2+］i变化的影响

目的研究银杏叶提取物对低氧复氧、H₂O₂和L-谷氨酸损伤时谷氨酸升高大鼠星形胶质细胞［Ca²⁺］_i的影响。方法钙荧光探针Fluo-3/AM标记胞浆内游离钙离子，激光扫描共聚焦显微镜测定［Ca²⁺］_i的变化。结果 在低氧复氧、H₂O₂以及高浓度的L-谷氨酸损伤后，外源性谷氨酸（27 μmol·L^-1）均不能引起培养乳大鼠星形胶质细胞正常的［Ca²⁺］_i升高，反而使［Ca²⁺］_i分别降低(3.3±1.6)%，(81±11)%和(81±7)%；损伤前预先给予GbE（10 mg·L^-1）不能明显改善星形胶质细胞的谷氨酸反应，但预先给予GbE（100 mg·L^-1）后，27 μmol·L^-1谷氨酸可使损伤的星形胶质细胞［Ca²⁺］_i分别升高(135±98)%，(117±93)%和(89±36)%。结论低氧复氧、H₂O₂以及高浓度的L-谷氨酸均能损伤星形胶质细胞的谷氨酸反应，影响神经细胞与胶质细胞的双向交流。GbE能明显逆转不同损伤后谷氨酸诱导星形胶质细胞［Ca²⁺］_i的异常变化，使星形胶质细胞在不同损伤时能维持正常功能，该作用可能与GbE的脑保护作用有关。     

人参皂苷Rg1及其肠内菌代谢产物Rh1对小鼠免疫细胞功能的影响

目的初探人参皂苷Rg₁及其肠内菌代谢产物Rh₁对正常小鼠免疫功能的影响。方法用Rh₁与Rg₁分别处理脾T细胞,B细胞及腹腔巨噬细胞(Mφ);MTT比色法测T和B细胞增殖能力;中性红比色法测Mφ的吞噬功能;Griess法测Mφ释放NO的水平。结果Rh₁能促进脾细胞增殖、下调Con A诱导的T细胞增殖;Rh₁与Rg₁对LPS诱导的B细胞增殖均无明显作用;Rg₁和Rh₁能提高Mφ的吞噬能力和促进NO的释放。结论Rg₁及其代谢产物Rh₁可共同作用于T细胞和Mφ而产生免疫调节作用。     

研究药物对肿瘤细胞代谢的新方法──灌注细胞31P核磁共振谱

为连续观察药物对细胞代谢的影响,用含紫杉醇的灌注液对人口腔上皮癌KB细胞和人结肠癌HCT-8细胞在灌注条件下进行了细胞³¹P谱测定,从两种细胞在未给药、给药以及停药后的灌注条件下获得的代谢图谱中发现,紫杉醇使KB细胞和HCT-8细胞的ATP代谢水平均有升高,但KB细胞的ATP升高更为明显;同样剂量的长春新碱使KB细胞代谢中的ATP峰的改变不明显,推测可能与它们的作用机制不同有关。研究结果表明,灌注细胞³¹P谱测试法对观察药物对细胞代谢的作用是独特的。     

四肽FMRFa对大鼠心室肌Na+/Ca2+交换的抑制

目的　研究四肽FMRFa对大鼠单个心室肌细胞Na⁺/Ca²⁺交换的作用。方法　用膜片钳全细胞记录法测定成年大鼠心室肌细胞Na⁺/Ca²⁺交换电流(I_Na⁺/Ca²⁺)和其他离子通道电流。结果　FMRFa对大鼠心室肌细胞I_Na⁺/Ca²⁺呈浓度依赖性抑制,100μmol·L^-1浓度时抑制内向和外向I_Na⁺/Ca²⁺密度分别达60.1%和56.5%,对内向电流及外向电流的IC₅₀分别为20μmol·L^-1和34μmol·L^-1。FMRFa5μmol·L^-1抑制I_Na⁺/Ca²⁺内向和外向电流密度分别为38.7%和34.9%,但FMRFa5μmol·L^-1及20μmol·L^-1对L型钙电流、钠电流、瞬时外向电流和内向整流钾电流均无显著抑制作用。结论　FMRFa对大鼠心室肌细胞是一个特异性Na⁺/Ca²⁺交换抑制剂。     

前胡香豆素对肾型高血压大鼠左室肥厚及心肌胞内钙、Na+,K+-ATP酶和Ca2+,Mg2+-ATP酶活性的影响

目的研究前胡香豆素组分对肾型高血压左室肥厚的预防和逆转作用及机制。方法用两肾一夹肾型高血压左室肥厚大鼠(RHR)模型,测定前胡香豆素组分对其血压、左室湿重、心肌细胞面积、胞内静息钙及胞膜和线粒体ATP酶活性的影响。结果前胡香豆素组分(30 mg·kg^-1·d^-1,ig)预防组及逆转组大鼠血压、左室湿重/体重均较肥厚组明显降低;左室心肌细胞面积、胞内静息钙均较肥厚组降低;对KCl致钙浓度升高亦明显低于肥厚组;两组均可增加心肌细胞膜及线粒体Na⁺,K⁺-ATP酶和Ca²⁺,Mg²⁺-ATP酶活性。结论前胡香豆素组分可预防及逆转RHR左室肥厚,减少心肌细胞内钙含量,增加ATP酶活性。     

慢性温和不可预知应激抑郁模型大鼠脑组织1H-NMR代谢组学研究

目的 采用高分辨核磁共振¹H谱（¹H-NMR）代谢组学技术研究慢性温和不可预知应激（CUMS）抑郁大鼠脑组织中代谢物及代谢通路的变化，探讨抑郁症的发病机制。方法 12只雄性SD大鼠随机分为模型组和对照组，采用CUMS对模型组大鼠进行为期4周的造模，进行称体质量、旷场实验和糖水偏爱实验验证模型是否成功，造模结束后收集大鼠脑组织。采用两相提取法（甲醇/氯仿/水）对脑组织进行提取，得到水溶性和脂溶性代谢物。应用¹H-NMR技术结合多元统计和代谢通路分析筛选出与抑郁相关的脑内差异代谢物，并构建其代谢通路。结果 行为学数据显示，与对照组比较，模型组大鼠的体质量、糖水偏爱率、旷场的穿格数和直立次数均显著降低（P<0.05），显示了抑郁状态。在大鼠脑组织的¹H-NMR图谱中共指认出35种内源性代谢产物。脑组织中水溶性和脂溶性代谢物主成分分析（PCA）均显示模型组与对照组分开，与行为学结果一致，表明造模成功；OPLS-DA分析找到9个水溶性差异代谢物和6个脂溶性差异代谢物。就水溶性代谢物而言，与对照组比较，模型组中肌酐、谷氨酰胺、牛磺酸和γ-氨基丁酸含量显著增加（P<0.05、0.01、0.001），丙二醇、谷氨酸、亮氨酸、缬氨酸和赖氨酸含量显著降低（P<0.05、0.01、0.001）。就脂溶性代谢物而言，与对照组比较，模型组-（CH₂） n和-N （Me₃）₃含量显著升高（P<0.05、0.001），胆固醇的C18/19甲基、R-CH₃、CH₂OPO₂-、-CH=CH-含量显著降低（P<0.05、0.01、0.001）。与对照组比较，CUMS造模后5条代谢通路发生显著变化：缬氨酸、亮氨酸和异亮氨酸生物合成，牛磺酸和亚硫磺酸代谢，丙氨酸、天冬氨酸和谷氨酸代谢，糖降解和糖异生通路和丙酮酸代谢。结论 运用¹H-NMR代谢组学技术结合多元统计分析和代谢通路分析，阐明抑郁症的发病机制与能量代谢、氨基酸代谢和神经递质合成等相关。     

Evaluation of the absorption, excretion, and metabolism of the antihypertensive agent RWJ-26899 in male and female CR Wistar rats and Beagle dogs.

The absorption, excretion and metabolism of N-(2, 6-dichlorophenyl)-beta-[[(1-methylcyclohexyl)methoxylmethyl]-N-(phenylmethyl)-1-pyrrolidineethanamine (RWJ-26899; McN-6497) has been investigated in male and female CR Wistar rats and beagle dogs. Radiolabeled [14C] RWJ-26899 was administered to rats as a single 24 mg/kg suspension dose while the dogs received 15 mg/kg capsules. Plasma (0-36 h; rat and 0-48 h; dog), urine (0-192 h; rat and dog) and fecal (0-192 h; rat and dog) samples were collected and analyzed. There were no significant gender differences observed in the data. The terminal half-life of the total radioactivity for rats from plasma was estimated to be 7.7 +/- 0.6 h while for dogs it was 22.9 +/- 4.4 h. Recoveries of total radioactivity in urine and feces for rats were 8.7 +/- 2.9% and 88.3 +/- 10.4% of the dose, respectively. Recoveries of total radioactivity in urine and feces for dogs were 4.1 +/- 1.4% and 90.0 +/- 4.7% of the dose, respectively. RWJ-26899 and a total of nine metabolites were isolated and tentatively identified in rat urine, and fecal extracts. Unchanged RWJ-26899 accounted for approximately 1% of the dose in rat urine and 8% in rat feces. RWJ-26899 and a total of four metabolites were isolated and identified in dog urine, and fecal extracts. Unchanged RWJ-26899 accounted for approximately 1% of the dose in urine and 63% in feces in dog. Five proposed pathways were used to describe the metabolites found in rats: N-oxidation, oxidative N-debenzylation, pyrrolidinyl ring hydroxylation, phenyl hydroxylation and methyl or cyclohexyl hydroxylation. Two biotransformation pathways in dogs are proposed: N-oxidation and methyl or cyclohexyl ring hydroxylation.     

Metabolism and disposition of [(14)C]1-nitronaphthalene in male Sprague-Dawley rats.

In rats and mice, 1-nitronaphthalene (1-NN) produces both lung and liver toxicity. Even though these toxicities have been reported, the metabolism and disposition of 1-NN have not been elucidated. Therefore, studies were performed to characterize its fate after i.p. and i.v. administration to male Sprague-Dawley rats. After i.p. administration of [(14)C]1-NN (100 mg/kg; 60 microCi/kg), 84% of the dose was eliminated in the urine and feces by 48 h. At 96 h, 60% of the dose was recovered in the urine, 32% in the feces, and 1% collectively in the tissues, blood, and gastrointestinal contents. The terminal phase rate constant (k(term)) of 1-NN was 0.21 h(-1), the terminal phase half-life (T(1/2,term)) was 3.40 h, and the systemic bioavailability was 0.67. When administered i.v. (10 mg/kg; 120 microCi/kg), 85% of the dose was eliminated in the urine and feces by 24 h. At the end of the study (96 h), 56% of the dose was recovered in the urine, 36% in the feces, and 1% collectively in the tissues, blood, and gastrointestinal contents. Interestingly, 88% of the dose was secreted into bile by 8 h. The k(term) was 0.94 h(-1) and the T(1/2,term) was 0.77 h. The major urinary metabolite after both routes of administration was N-acetyl-S-(hydroxy-1-nitro-dihydronaphthalene)-L-cysteine. Other urinary metabolites identified include hydroxylated, dihydroxylated, glucuronidated, sulfated, and reduced metabolites, as well as dihydrodiol. The major biliary metabolite was hydroxy-glutathionyl-1-nitro-dihydronaphthalene. These data show that 1-NN undergoes extensive metabolism and enterohepatic recirculation, and the majority of the dose is eliminated in the urine.     

来曲唑在大鼠体内药代动力学的性别差异(英文)

目的:研究来曲唑(Letr)药动学性别差异性。方法:ig Letr 2mg/kg后,测定在雄、雌性大鼠血浆、组织中浓度及粪、尿中回收率。结果:ig Letr 6 h以后,雄鼠中血药浓度显著低于雌鼠,如给药24,36,48和72h,雌鼠血药浓度分别为雄鼠的3.3,5.6,10.5和7.4倍。雄鼠AUC也仅为雌鼠的1/3,其半衰期分别为10.5和40.4h。120h内,雌鼠尿和粪中排泄分数分别为5.78％±1.40％和6.61％±1.10％,而雄鼠仅分别为1.30％±0.59％和0.87％±0.31％;给药后24h,雌鼠组织中药物浓度显著高于雄鼠。结论:Letr在大鼠体内的药动学存在较大的性别差异。     

Evaluation of the excretion, and metabolism of the cardiotonic agent bemoradan in male rats and female beagle dogs.

The excretion and metabolism of (+/-) [6-(3,4-dihydro-3-oxo-1,4[2H]-benzoxazine-yl)-2,3,4,5-tetrahydro-5-methylpyridazin-3-one] (bemoradan; RWJ-22867) have been investigated in male Long-Evans rats and female beagle dogs. Radiolabeled [14C] bemoradan was administered to rats as a singkle 1 mg/kg suspension dose while the dogs received 0.1 mg/kg suspension dose. Plasma (0-24 h; rat and dog), urine (0-72 h; rat and dog) and fecal (0-72 h; rat and dog) samples were collected and analyzed. The terminal half-life of the total radioactivity for rats from plasma was estimate to be 4.3 +/- 0.1 h while for dogs it was 7.5 +/- 1.3 h. Recoveries of total radioactivity in urine and feces for rats were 49.1 +/- 2.4% and 51.1 +/- 4.9% of th dose, respectively. Recoveries of total radioactivity in urine and feces for dogs were 56.2 +/- 12.0% and 42.7 V 9.9% of the dose, respectively. Bemoradan and a total of nine metabolites were isolated and tentatively identified in rat and dog plasma, urine, and fecal extracts. Unchanged bemoradan accounted for approimately < 2% of the dose in rat urine and 20% in rat feces. Unchanged bemoradan accounted for approximately 5% of the dose in urine and 16% in feces in dog. Six proposed pathways were used to describe the metabolites found in rats and dogs: pyridazinyl oxidations, methyl hydroxylation, hydration, N-oxidation, dehydration and phase II conjugations.     

Disposition of a low dose of 14C-bisphenol A in male rats and its main biliary excretion as BPA glucuronide.

Bisphenol A (BPA) is a weak xenoestrogen mass-produced with potential human exposure. The disposition of bisphenol A in male Fischer-344 (F344) rats dosed orally (100 or 0.10 mg/kg) or intravenously (0.10 mg/kg) was determined. Smaller amounts of the dose appeared in the urine. The main excretion route was feces in rats irrespective of dose and administration route. The biliary excretion during 6 h was 58-66% after iv dosing and 45-50% after oral dosing at 0.10 mg 14C-BPA/kg. Toxicokinetic parameters obtained from 14C-BPA-derived radioactivity in blood were the terminal elimination half-life, t1/2beta = 39.5 h, and total body clearance, CLtot = 0.52 l/h/kg after iv dosing of 0.10 mg 14C-BPA/kg to male rats. The blood concentration reached its maximum of 5.5 ng-eq/ml at 0.38 h after oral dose. AUC(0-6 h), AUC(0-48 h), and AUCinf of 14C-BPA-derived radioactivity, were 34, 118, and 192 ng-eqh/ml for the iv dose and 18, 102, and 185 ng-eqh/ml for the oral dose, respectively. The oral bioavailability of F(0-6 h), F(0-48 h), and Finf were 0.54, 0.86, and 0.97, respectively. The 14C-BPA-derived radioactivity was strongly bound to plasma protein (free fraction, fu = 0.046) and preferentially distributed to the plasma with a blood/plasma ratio of 0.67. From the bile of male rats orally dosed at 100 mg/kg, we have isolated and characterized BPA glucuronide (BPA-gluc) by ESI/MS, 1H and 13C NMR spectroscopy. HPLC analysis showed that BPA-gluc was the predominant metabolite in bile and urine. Unchanged BPA was mostly detected in feces. These results suggest that BPA is mainly metabolized to BPA-gluc and excreted into feces through the bile and subject to enterohepatic circulation in rats irrespective of dose and administration route.     

Toxicokinetics of 14C-endosulfan in male Sprague-Dawley rats following oral administration of single or repeated doses

Endosulfan (ES), an organochlorine (OC) insecticide that belongs to the cyclodiene group, is one of the most commonly used pesticides to control pests in vegetables, cotton, and fruits. The toxicokinetics of 14C-endosulfan following oral administration of a single dose of 5 mg/kg body weight was investigated in male Sprague-Dawley rats. Three rats were sacrificed 30 min, 1 h, 2 h, 4 h, and 8 h after dosing. 14C-endosulfan radioactivity was detected in all tissues at each time point. In a separate experiment urine and feces were collected for 96 h. The total radioactivity recovered in the excreta for 4 days was 106.8% +/- 26.2%, with fecal elimination the major route of elimination route (94.4% +/- 21.4%). The cumulative excretion in the urine for 4 days was 12.4% +/- 4.8%. Radioactivity 8 h after administration was highest in gastrointestinal (GI) tract tissue (20.28 +/- 16.35 mg ES eq./L) and lowest in muscle (0.18 +/- 0.06 mg ES eq./L). The toxicokinetic parameters obtained from 14C-endosulfan-derived radioactivity in blood were distribution half-life (T1/2 x) = 31 min and terminal elimination half-life (T1/2 y) = 193 h. Blood concentration reached its maximum (Cmax) of 0.36 +/- 0.08 mg ES eq./L 2 h after the oral dose. Endosulfan was rapidly absorbed into the GI tract in rats, with an absorption rate constant (ka) of 3.07 h(-1).     

Absorption and disposition of aluminum in the rat

The kinetics of aluminum were determined in the rat. Intravenous bolus and oral doses of 8.1-mg/kg of aluminum as the chloride salt were administered to six rats. Serial blood samples and total urine and feces were collected and assayed for aluminum by atomic absorption spectrophotometry. The fraction absorbed orally (mean +/- SEM) was 0.27 +/- 0.03; the half-life was 5.29 +/- 0.47 h; the steady-state volume of distribution was 38.4 +/- 6.4 mL/kg, and the clearance was 8.87 +/- 1.76 mL X h-1 X kg-1. It was found that aluminum did not significantly penetrate the cellular components of blood. Plasma protein binding was determined to be approximately 98%. Sixty percent of the intravenous dose was excreted in the urine and the remaining 40% was excreted in the feces.     

Disposition and metabolism of cetrorelix, a potent luteinizing hormone-releasing hormone antagonist, in rats and dogs.

Disposition and metabolism of cetrorelix was studied in intact and bile duct-cannulated rats and dogs after s.c. injection. An s.c. dose of 0.1 mg/kg [(14)C]cetrorelix was rapidly and completely absorbed in rats. T(max) in plasma and most tissues was at 2 h. Radioactivity at the injection site in rats declined to 10% by 24 h. The extent of (14)C absorption in rats calculated from excretion until 264 h was 94%. Exposure of the target organ pituitary gland was demonstrated with a time course similar to plasma but on a higher level. Rats excreted 69.6% of radioactivity via feces and 24. 3% into urine. Excretion was nearly complete within 48 h. No enteral reabsorption was detected. In dogs t(max) in plasma was 1.3 h. (14)C- and cetrorelix-plasma levels were similar until 24 h, indicating a negligible amount of metabolites. A dose of 1 mg/kg in dogs showed an increasing influence of a slow absorption phase (flip-flop). In dogs equal amounts of the (14)C dose were found within 192 h in feces and urine, 46 and 48%, respectively. In urine of both species, only intact cetrorelix was detected. In bile and feces of both species qualitatively the same metabolites were found, characterized as truncated peptides of the parent decapeptide. The major metabolite occurring in bile of both species was the (1-7)heptapeptide. The amounts of the (1-4)tetrapeptide in feces of rats but not in that of dogs increase with time, suggesting additional degradation of the peptide in the gastrointestinal tract of rats by enteric metabolization.     

Disposition of 14C-alpha-cyclodextrin in germ-free and conventional rats

The absorption, disposition, metabolism, and excretion of uniformly (14)C-labeled alpha-cyclodextrin ((14)C-alpha-CD) was examined in four separate experiments with Wistar rats. In Experiment 1, (14)C-alpha-CD (25 microCi, 50 mg/kg bw) was administered intravenously to four male and four female conventional rats. In Experiment 2, (14)C-alpha-CD (25 microCi, 200 mg/kg bw) was given by gavage to four male and four female germ-free rats. In Experiments 3 and 4, (14)C-alpha-CD was given to groups of four male and four female conventional rats by gavage at different dose levels (100 microCi, 200 mg/kg bw; 25 microCi, 200 and 100 mg/kg bw). In all experiments, (14)C was measured in respiratory CO(2), urine, and feces over periods of 24-48 h, and in the contents of the gastrointestinal tract, blood, main organs, and residual carcass at termination of the experiments. The chemical identity of the (14)C-labeled compounds was examined by HPLC in blood (Experiment 1), urine (Experiments 1-4), feces (Experiments 2-4), and samples of intestinal contents (Experiments 2 and 4). Recovered (14)C was expressed as percentage of the administered dose. Experiment 1 showed that intravenously administered alpha-CD is excreted rapidly with urine. During the first 2h after dosing, plasma (14)C levels decreased rapidly (t(1/2), 26 and 21 min in male and female rats, respectively). About 13% of the administered (14)C dose (range 4.6-30.6) was detected in the feces, respiratory CO(2), organs, and carcass at the end of the experiment, i.e., 24 h after dosing. The presence of about 1.9% in the intestinal contents and feces suggests that a certain fraction of systemic alpha-CD is eliminated with the bile or saliva. Conclusive evidence, either positive or negative, for a hydrolysis and further metabolism of a small fraction of the administered alpha-CD by the enzymes of the mammalian body could not be gained from this experiment. Upon oral administration of (14)C-alpha-CD to germ-free rats (Experiment 2), about 1.3% of the label expired as CO(2) within 24 h. In the urine collected from 0 to 8 h after dosing, (14)C-alpha-CD was the only radiolabeled compound detected. The amounts of alpha-CD detected in the urine suggest that on average about 1% of an oral dose is absorbed in rats during small-intestinal passage. In conventional rats (Experiments 3 and 4), a delayed appearance of respiratory (14)CO(2) was observed which is attributed to the non-digestibility of alpha-CD and its subsequent microbial fermentation in the cecum and colon. In the urine collected at 4 h after dosing, a small amount of unchanged (14)C-alpha-CD was detected which confirms that about 1% of the ingested alpha-CD is absorbed intact and is excreted via the kidneys. No (14)C-alpha-CD was found in the feces. It is concluded from the data that ingested (14)C-alpha-CD is not digested in the small intestine of rats but is fermented completely by the intestinal microbiota to absorbable short-chain fatty acids. Therefore, the metabolism of alpha-CD resembles closely that of resistant starch or other fermentable dietary fibers.     

Pharmacokinetics of pentaerythritol tetranitrate following intra-arterial and oral dosing in the rat

The pharmacokinetics of pentaerythritol tetranitrate (2,2-bis(hydroxymethyl)-1,3-propanediol tetranitrate, 1) were studied in rats following a single intra-arterial or oral dose (2 mg/kg) of the 14C-labeled drug. Blood levels of the tetranitrate and its metabolites were determined using a thin-layer radiochromatographic procedure. The apparent systemic clearance of 1 was 0.61 +/- 0.16 L/min/kg (mean +/- SD, n = 6) which exceeded the value of normal cardiac output in rats. The steady-state volume of distribution was 4.2 +/- 1.1 L/kg (n = 6), and the elimination half-life was estimated at 5.8 +/- 0.6 min (n = 6). Blood levels of 1 were only detectable (higher than 4.0 ng/mL) in three of the six rats examined after the oral dose. The trinitrate derivative (2,2-bis(hydroxymethyl)-1,3-propanediol trinitrate, 2) the active metabolite of 1, was not detectable following oral dosing with the tetranitrate. The oral bioavailability of 1 was in the range of 0-8%. In spite of the low water solubility of 1 (i.e., 1 microgram/mL), a rather high fraction of the radioactive oral dose [25.7 +/- 10.3% (n = 4) versus 62.4 +/- 14.5% (n = 4) from the intra-arterial dose] was recovered in the urine. A significant portion of the intra-arterial dose (32.7 +/- 11.0%, n = 4) was eliminated in feces, indicating enterohepatic recycling of radioactivity. Analysis of the metabolite pattern in urine indicated extensive metabolism of 1, 2, and the dinitrate derivative 3 (2,2-bis(hydroxymethyl)-1,3-propanediol dinitrate). Less than 0.2% of the dose was recovered as unchanged drug and 2 following either route of administration.