Online ISSN: 1884-4111 Print ISSN: 0033-8303
Radioisotopes 70(4): 261-270 (2021)


黒毛和種における安定セシウム単回投与後の体内動態Pharmacokinetics of Stable Caesium after Single Administration of Caesium Chloride in Japanese Black Cattle

1北里大学獣医学部Kitasato University, School of Veterinary Medicine

2家畜改良センターNational Livestock Breeding Center

受付日:2020年10月19日Received: October 19, 2020
受理日:2020年11月9日Accepted: November 9, 2020
発行日:2021年5月15日Published: May 15, 2021

黒毛和種(n=20)に塩化セシウム(133CsCl: 20 mg/kg)水溶液を静脈内投与群および経口投与群にそれぞれ投与し安定セシウム(SCs)の薬物動態学的(PK)パラメータを明らかにした。投与前から投与後最長182日までの生体試料中SCsはICP-MSで測定した。各群より得られたPKパラメータ(mean±sd)は以下の通り。濃度-時間曲線下面積(AUC; μg/ L·h):0.54±0.06(IVp),0.42±0.05(POp),0.87±0.11(IVb),および0.71±0.33(POb),平均滞留時間(MRT; 日);20.9±3.2(IVp),19.3(POp) ±2.9,24.7±3.6(IVb),および23.6±5.2(POb),生体内利用率(F%);82±29および83±38,クリアランス(CL; mL/min/kg):0.46±0.05(IVp),0.49±0.06(POp),0.29±0.04(IVb),および0.31±0.08(POb),分布容積(Vd; L/kg):3.3(Vdp)および4.4(Vdb)。終末相の生物学的半減期(T1/2)約30日と推定された。投与量に対する回収率(%)は尿で28±6(IV)および28±8(PO),糞便で85±21(IV)および122±42%(PO)であった。いずれの投与経路でも生体試料中SCs濃度は同様な二相性の分布および消失プロファイルを示し,これらはバックグラウンドレベルを考慮したコンパートメントモデルにより説明された。今回求められた動態パラメータより,長期間放射性セシウムに暴露された環境からの黒毛和種の体内動態を推定することが可能となる。

Pharmacokinetic (PK) parameters of stable caesium (SCs) were determined in adult Japanese Black Cattle (JBC, n=20). They were divided into two groups, i.e, intravenous (IV) and oral (PO) administration groups, and each of them was administered 133CsCl solution (20 mg/kg b.w.). SCs in biological samples was measured by ICP-MS, and their concentration-time courses were monitored for 182 days. The PK parameters determined in plasma and blood in each group were as follows (mean±SD); area under the concentration-time curve (AUC;µg/L·h): 0.54±0.06 (IVp), 0.42±0.05 (POp), 0.87±0.11 (IVb), and 0.71±0.33 (POb), mean residence time (MRT; day); 20.9±3.2 (IVp), 19.3±2.9 (POp), 24.7±3.6 (IVb), and 23.6±5.2 (POb), bioavailability (F%); 82±29 and 83±38, clearance (CL; mL/min/kg): 0.46±0.05 (IVp), 0.49±0.06 (POp), 0.29±0.04 (IVb), and 0.31±0.08 (POb), and distribution volume (Vd; L/kg) was 3.3 (Vdp) and 4.4 (Vdb). The biological half-life of the terminal elimination phase (T1/2) was estimated to be approximately 30 days. The urine recovery for the dose was 28±6 (IV) and 28±8 (PO), and the fecal recovery was 85±21 (IV) and 122±42% (PO). The time course via both routes of administration showed similar biphasic distribution and elimination profile in any biological samples and elucidated by compartment analysis with consideration of background level. Based on the PK parameters, elimination profile of radioactive caesium (RCs) from the JBC kept long in the RCs contaminated area can be explained.

Key words: caesium; Japanese Black Cattle; pharmacokinetics; biological half-life; Fukushima Dai-ichi Nuclear Power Plant Accident

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