Dragsted L O, Frandsen H, Reistad R, Alexander J, Larsen J C
Danish National Food Agency, Institute of Toxicology, Søborg, Denmark.
Carcinogenesis. 1995 Nov;16(11):2785-93. doi: 10.1093/carcin/16.11.2785.
Untreated and Aroclor 1254-pretreated male Wistar rats were given a single dose of 1.0 mg/kg body weight of randomly tritium-labelled 2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine (3H-PhIP) by oral intubation. Urine and faeces were collected at 24, 48 and 72 hours after dosing, and total radioactivity determined. At 2, 4, 6, 16, 26, 48 and 72 h, animals were killed and several organs, including liver, bladder, lungs, kidney, stomach, large and small intestines, heart, thigh muscles, spleen and blood were collected for DNA extraction and for determination of total radioactivity. Highest total radioactivity at 2 h was not unexpectedly observed in the stomach, small intestines and bladder, whereas radiolabels corresponding to approximately 2.5 nmol PhIP/g of kidney and liver showed the highest levels observed at 24 h. Several tissues, including blood, plasma, liver and muscles had a slightly bimodal time-distribution of radioactivity showing a second peak at 16-24 h. At 72 h after a single dose of PhIP, highest radioactivity was observed in the liver and the large intestine (0.4 nmol PhIP/g tissue), whereas most other organs, irrespective of pretreatment had levels at approximately 0.2 nmol/g of tissue. At earlier time points, Aroclor 1254-treated rats had lower amounts of radiolabel in all tissues. Radioactivity bound to DNA was determined by high sensitivity scintillation counting. In contrast to total radioactivity, DNA-associated radioactivity was generally higher in the Aroclor 1254-treated rats, most notably in the heart, but levels had decreased to approximately the same level in controls and in Aroclor 1254-treated rats at 72 h. DNA-binding was highest at 2-6 h after dosing, highest in the heart of Aroclor 1254-treated animals at 6 h (120 adducts/10(8) bases) followed by thigh muscle at 4-6 h (approximately 50 adducts/10(8) bases, irrespective of pretreatment). Levels were approximately 1.5-3 times lower in other organs at 2-6 h after dosing. At 72 h, radioactivity associated with DNA was again highest in the heart of Aroclor 1254-treated rats (20 adducts/10(8) bases) and 5-10 times lower in most other organs, approaching the detection limit. Total DNA was extracted from the livers of PhIP dosed rats at 4 ad 72 h. DNA was hydrolysed, affinity-concentrated, and analysed by liquid chromatography. A radiolabelled peak had identical retention time and UV-spectral characteristics as peaks isolated by affinity chromatography and HPLC of acid-hydrolysed synthetic PhIP-DNA and PhIP-deoxyguanosine adduct.(ABSTRACT TRUNCATED AT 400 WORDS)
对未处理的和经Aroclor 1254预处理的雄性Wistar大鼠，通过经口插管给予单剂量1.0毫克/千克体重的随机氚标记的2-氨基-1-甲基-6-苯基咪唑并[4,5-b]吡啶（3H-PhIP）。给药后24、48和72小时收集尿液和粪便，并测定总放射性。在2、4、6、16、26、48和72小时，处死动物，收集包括肝脏、膀胱、肺、肾、胃、大肠和小肠、心脏、大腿肌肉、脾脏和血液在内的多个器官用于DNA提取和总放射性测定。不出所料，给药后2小时胃、小肠和膀胱中的总放射性最高，而对应于约2.5纳摩尔PhIP/克肾脏和肝脏的放射性标记物在24小时时显示出最高水平。包括血液、血浆、肝脏和肌肉在内的多个组织的放射性呈现出轻微的双峰时间分布，在16 - 24小时出现第二个峰值。单剂量PhIP给药72小时后，肝脏和大肠中的放射性最高（0.4纳摩尔PhIP/克组织），而大多数其他器官，无论是否经过预处理，其水平约为0.2纳摩尔/克组织。在较早的时间点，经Aroclor 1254处理的大鼠所有组织中的放射性标记物含量较低。通过高灵敏度闪烁计数法测定与DNA结合的放射性。与总放射性相反，经Aroclor 1254处理的大鼠中与DNA相关的放射性通常较高，最明显的是在心脏中，但在72小时时，对照组和经Aroclor 1254处理的大鼠中的水平已降至大致相同。给药后2 - 6小时DNA结合最高，经Aroclor 1254处理的动物在6小时时心脏中的DNA结合最高（120个加合物/10⁸个碱基），其次是4 - 6小时时大腿肌肉中的（约50个加合物/10⁸个碱基，无论是否经过预处理）。给药后2 - 6小时，其他器官中的水平约低1.5 - 3倍。在72小时时，经Aroclor 1254处理的大鼠心脏中与DNA相关的放射性再次最高（20个加合物/10⁸个碱基），大多数其他器官中的水平低5 - 10倍，接近检测限。在4和72小时从经PhIP给药的大鼠肝脏中提取总DNA。DNA被水解、亲和浓缩，并通过液相色谱分析。一个放射性标记峰的保留时间和紫外光谱特征与通过亲和色谱和酸水解合成PhIP - DNA及PhIP - 脱氧鸟苷加合物的HPLC分离得到的峰相同。（摘要截短至400字）
