L-[1-13C]苯丙氨酸呼气试验定量检测肝脏功能动物实验研究

目的采用自行设计的小动物呼气试验模型进行大鼠L-[1-13C]苯丙氨酸呼气试验(13C-PheBT),以验证该实验方法的可行性和有效性,并提供有效的试验参数.方法280～290g的雄性SD大鼠20只,随机分为急性肝损伤组和正常对照组,每组10只,采用四氯化碳橄榄油灌胃染毒复制急性肝损伤模型,小动物呼气机进行机械通气制作呼气试验模型;按20mg/kg体重尾静脉弹丸给予13C-苯丙氨酸(13C-Phe),收集给药前和给药后1～60min呼出气样共29次气样,应用气体同位素比值质谱仪测定样品中13C丰度.结果13C排除时相曲线呈单峰,峰值多位于给药后2 min;急性肝损伤大鼠呼气试验参数13C排除速率常数(PheBT-K)为(2.45±0.25)×10-2 min-1,显著低于正常对照组(2.98±0.19)×10-2 min-1 (t=5.40,P＜0.001),而急性肝损伤大鼠呼出气中13C排除峰值和血清中丙氨酸转氨酶(ALT)、天冬氨酸转氨酶(AST)、总胆汁酸(TBA)、碱性磷酸酶(AKP)和总胆红素(TBIL)含量均显著高于正常对照组(t值分别为8.15,3.40,3.90,4.83和4.12,P＜0.05);13C快处置常数在两组间差异无显著性(t=0.58,P＞0.05);急性肝损伤大鼠PheBT-K与血清ALT和AKP活度以及TBA和TBIL水平呈负相关(r分别为-0.74、-0.73、-0.82和-0.67,P值均小于0.05),而与血清AST活度无相关性(r=0.16,P＞0.05).结论自行设计的小动物呼气试验模型是进行呼气试验基础研究的有效工具;动物PheBT-K是一项灵敏的分析指标.     

13C呼气试验:一种有益的消化系统疾病检测方法

稳定性核素13C呼气试验作为一种安全、简便、无创的检查.可以对脏器功能进行实时定量的评价,具有一定的敏感性和特异性,日益受到临床医生青睐.该文综述国内外13C呼气试验在消化系统疾病诊断领域的应用研究进展及其局限性,并对其发展作一展望.     

13C呼气试验:一种有益的消化系统疾病检测方法

稳定性核素13C呼气试验作为一种安全、简便、无创的检查.可以对脏器功能进行实时定量的评价,具有一定的敏感性和特异性,日益受到临床医生青睐.该文综述国内外13C呼气试验在消化系统疾病诊断领域的应用研究进展及其局限性,并对其发展作一展望.     

^13C呼气试验：一种有益的消化系统疾病检测方法

稳定性核素^13C呼气试验作为一种安全、简便、无创的检查，可以对脏器功能进行实时定量的评价，具有一定的敏感性和特异性，日益受到临床医生青睐。该文综述罔内外^13C呼气试验在消化系统疾病诊断领域的应用研究进展及其局限性，并对其发展作一展望。     

^13C呼气试验的临床应用价值与发展前景

^14C呼气试验曾受到广泛关注，但鉴于^4C长达5730年的半衰期，对其在人体进行诊断性检测的应用仍存在争议。相对而言，稳定核素^13C呼气试验即使用于孕妇或儿童也十分安全。^13C-尿素呼气试验已被广泛应用于营养学、药物代谢学以及消化系统各种疾病的诊断研究中。近年来，随着各种不同的^13C标记底物相继研发及其呼气试验在临床中研究的深入，呼气试验的一些不足不断被弥补。     

73例~13C-尿素呼气试验检测幽门螺杆菌的观察

本文论述利用幽门螺杆菌的内源性尿素酶可特异性分解尿素的特性,以85mg稳定同位素~(13)C标记的尿素为示踪剂,观察了73例患者在口服~(13)C-尿素前后30min内呼气中~(13)CO_2浓度的变化,探讨了该方法在诊断胃幽门螺杆菌的价值.实验方法:空腹进150ml试餐后服85mg~(13)C-尿素,分别收集给药前及给药后30min的呼气.用气体同位素比值质谱仪测定~(13)CO_2的千分差值(δ‰).以Ib值表示Ib=Ib_(30)—Ib_0.部分病人组织粘膜用Giemsa染色和快速尿素酶观察.结果:73例Ib从0.1～2.85;其中阴性(Ib<0.6)42例,Ib值从0.01～O.48;阳性及强阳性31例(Ib～≥O.6),Ib从0.73～2.85.胃幽门螺杆菌感染率为42%,其中十二指脂球部溃疡病人75%阳性,胃溃疡病人57%阳性.21例病人同时用三种方法检测结果为组织粘膜Giemsa染色6例显示阳性,阳性率29%;组织粘膜快速尿素酶法显示9例阳性,阳性率43%;~(13)C-尿素呼吸试验显示17例阳性,阳性率81%,X~2值>2,有明显差异性.     

^13C—辛酸呼吸试验测定糖尿病胃固体排空功能的重复性研究

目的 观察^13C-辛酸呼吸试验测定糖尿病患者胃固体排空时间及其变异性,以及心自主神经病变和病理性胃排空状况对其的影响。方法 9例对照者和15例糖尿病患者[平均糖基化血红蛋白（HbA1c)7.8%]1周内行2次^13C-辛酸呼吸试验,采用非线性回归法计算半排空时间（t1/2)和缓慢期时间（tlag)同时采用心自主神经功能试验判断有无心自主神经病变。结果 对照组t1/2批内CV为11．7％,tlag批内CV为19．4％,糖尿病患者t1/2批内CV为17．8％,tlag批内CV为28．2％,对照者和糖尿病患者间差异无显著性。t1/2和tlag的批内CV在糖尿病患者伴有无心自主神经病变之间以及在正常胃排空时间和延迟性胃排空时间之间差异无显著性。结论 ^13C-辛酸呼吸试验测定胃固体排空功能有较高的重复性,并不受心自主神经病变和病理性胃排空的影响。     

^13C呼气试验—诊断和流行病学研究的工具

本文简述了~(13)C和~(14)C呼气试验的原理、用途、优点及发展过程。~(13)C-尿素呼气试验可以快速无损伤地检测受试者胃及十二指肠是否存在与其炎症、溃疡发病密切相关的幽门弯曲菌感染。因此它可用于抗溃疡病药物疗效的评估,并可在胃部炎症、溃疡及恶性肿瘤的流行病学研究中广泛应用。     

~（13）C－尿素呼气试验的方法学改进

１３Ｃ－尿素呼气试验是一种无创诊断幽门螺杆菌感染的好方法，但成本较高．我们探讨了１３Ｃ－尿素的给药剂量、收集呼气样品的时间以及呼气样品平均化处理等因素对降低检测成本的可能性．结果表明，对于一般成人给予１００ｍｇ１３Ｃ－尿素（儿童为６０ｍｇ）．收集给药后５０分钟内的４次呼气样品，经样品混合平均化后可获得满意结果．     

Enzymatic synthesis of [1-11C]pyruvic acid, L-[1-11C]lactic acid and L-[1-11C]alanine via DL-[1-11C]alanine

L-[1-11C]Lactic acid was prepared enzymatically from [1-11C]pyruvic acid by way of DL-[1-11C]alanine, using remote, semiautomated procedures. The DL isomers of alanine were prepared by a modification of the Bucherer-Strecker reaction from no-carrier-added (NCA) hydrogen [11C]cyanide. The enantiomer mixture was transformed to [1-11C]pyruvic acid by successive elution through columns of (a) immobilized D-amino acid oxidase (D-AAO)/catalase and (b) immobilized L-alanine dehydrogenase (L-AID) or L-amino acid oxidase (L-AAO/catalase). [1-11C]-Pyruvic acid was subsequently converted to L-[1-11C]lactic acid by passage through a L-lactic dehydrogenase (L-LDH) column. L-[1-11C]Alanine and [1-11C]-pyruvic acid were separated chromatographically by way of a cation-exchange column (AG50W-X2, H+ form). Typically the synthesis time was 35-40 min after cyclotron production of hydrogen [11C]cyanide (400 mCi), with radiochemical yields of 25 mCi (25%) for L-[1-11C]lactic acid, 35 mCi (29%) for [1-11C]pyruvic acid, and 20 mCi (20%) for L-[1-11C]alanine. The use of immobilized enzymes eliminates the possibility of protein contamination and assures the production of sterile, pyrogen-free products, allowing for rapid and effective regio- and stereo-specific transformations.     

Synthesis of no-carrier-added L- and D-[1-11C]-DOPA

No-carrier-added DL-[1-11C]-DOPA has been synthesized by carboxylation of an alpha-lithioisocyanide with a radiochemical yield of up to 15% without correction for decay. The total synthesis time is 30 min. The resolution of the D- and L-isomers was accomplished within 16 min by HPLC using a chiral stationary phase and a phosphate buffer of pH 4.5 as eluent.     

Localized proton NMR observation of [3-13C]lactate in stroke after [1-13C]glucose infusion.

To assess whether elevated lactate in stable stroke is being actively produced from blood glucose localized 1H NMR stimulated echo spectra were obtained from a patient in the region of a 32-day-old cortical infarct before and 60-100 min after infusion of [1-13C]glucose. Prior to the infusion the spectrum from the region of the infarct contained an elevated resonance from C3 lactate and a greatly reduced resonance from N-acetyl groups relative to an unaffected contralateral region. After the infusion two additional resonances were observed at 62 and -64 Hz relative to the unlabeled resonance of C3 lactate which were assigned on the basis of chemical shift and relative intensity to [3-13C]lactate. The [3-13C]lactate fractional enrichment in the infarct region was measured to be 32% which is within error one-half the average [1-13C]plasma glucose enrichment during the postinfusion NMR measurement. The result suggests that the stroke lactate pool was completely derived from infused glucose.     

Validation of the lactose-[13C]ureide breath test for determination of orocecal transit time by scintigraphy.

The breath test using oral administration of a 13C-labeled substrate, lactose-ureide (LU), to measure orocecal transit time (OCTT) was validated against 99mTc-scintigraphy. Although LU is not absorbed in the human small intestine, colonic bacteria readily metabolize LU, producing 13C-labeled CO2. The time at which 13CO2 appears in breath corresponds to the OCTT. METHODS: Twenty-two healthy volunteers ingested a meal labeled with 99mTc and 13C-LU. Scintigraphy was performed over 8 h at time intervals of 10 or 15 min. OCTT with scintigraphy was defined as the time at which at least 10% of the label had entered the colon. Breath samples were obtained every 10-15 min for 10 h and measured by isotope ratio mass spectrometry. OCTT was defined as the time of first significant increase above baseline. The results were compared using correlation and Altman-Bland statistics. RESULTS: OCTT results from scintigraphy (mean OCTT = 283+/-53 min) and breath test (mean OCTT = 292+/-58 min) correlated well (r = 0.94). Altman-Bland statistics showed close agreement between scintigraphy and breath test. No significant difference between male and female subjects was observed. CONCLUSION: The breath test using 13C-LU is a valid alternative to scintigraphy techniques for measuring OCTT.     

13C NMR study of the generation of C2- and C3,-deuterated lactic acid by tumoral pancreatic islet cells exposed to D-[1-13C]-, D-[2-13C]- and D-[6-13C]-Glucose in 2H2O

Tumoral pancreatic islet cells of the RIN5mF line were incubated for 120 min in media prepared in ²H₂O and containing D -[1-¹³C]glucose, and D -[2-¹³C]glucose, and D -[6-¹³C]glucose. The generation of C₂- and C₃- deuterated lactic acid was assessed by ¹³C NMR. The interpretation of experimental results suggests that a) the efficiency of deuteration on the C₁ of D-fructose 6-phosphate does not exceed about 47% and 4% in the phosphoglucoisomerase and phosphomannoisomerase reactions, respectively; b) approximately 38% of the molecules of D -glyceraldehyde 3-phosphate generated from D -glucose escape deuteration in the sequence of reactions catalyzed by triose phosphate isomerase and aldolase; and c) about 41% of the molecules of pyruvate generated by glycolysis are immediately converted to lactate, the remaining 59% of pyruvate molecules undergoing first a single or double back-and-forth interconversion with L -alanine. It is proposed that this methodological approach, based on high resolution ¹³C NMR spectroscopy, may provide novel information on the regulation of back-and-forth interconversion of glycolytic intermediates in intact cells as modulated, for instance, by enzyme-to-enzyme tunneling.     

Comparison of L-[1-11C]methionine and L-methyl-[11C]methionine for measuring in vivo protein synthesis rates with PET

To evaluate the feasibility of using either L-[1-11C]-methionine or L-[methyl-11C]methionine for measuring protein synthesis rates by positron emission tomography (PET) in normal and neoplastic tissues, distribution and metabolic studies with 14C- and 11C-labeled methionines were carried out in rats bearing Walker 256 carcinosarcoma. The tissue distributions of the two 14C-labeled methionines were similar except for liver tissue. Similar distribution patterns were observed in vivo by PET using 11C-labeled methionines. The highest 14C incorporation rate into the protein-bound fraction was found in the liver followed by tumor, brain, and pancreas. The incorporation rates in liver and pancreas were different for the two methionines. By chloroform-methanol fractionation of these four tissues, in liver significantly different amounts of 14C were observed in macromolecules. Also in brain tissue slight differences were found. By HPLC analyses of the protein-free fractions of plasma, tumor, and brain tissue at 60 min after injection, for both methionines several 14C-labeled metabolites in different amounts, were detected. About half of the 14C-labeled material in the protein-free fraction was found to be methionine. In these three tissues the amount of nonprotein metabolites and [14C]bicarbonate amount ranged from 10% to 17% and 12% to 15% for L-[1-14C]methionine and L-[methyl-14C]methionine, respectively. From these results it can be concluded that the minor metabolic pathways have to be investigated in order to quantitatively model the protein synthesis by PET.     

PET studies with L-[1-11C]tyrosine, L-[methyl-11C]methionine and 18F-fluorodeoxyglucose in prolactinomas in relation to bromocryptine treatment

Aspects of metabolism in prolactinomas were investigated by positron emission tomography using L-[1-11C]tyrosine, L-[methyl-11C]methionine and 18F-fluorodeoxyglucose (18FDG). Using L-[1-11C]tyrosine, four patients were monitored prior to and 18 h after an injection of 50 mg bromocriptine. At 18 h after bromocriptine intervention, L-[1-11C]tyrosine uptake into tumour was reduced with 28% (P less than 0.07). A correlation analysis of the bromocriptine-induced decrease in L-[1-11C]tyrosine uptake and the reduction of serum prolactin levels indicated that the action of bromocriptine on prolactin synthesis and prolactin release is not coupled. In the untreated situation, the four patients were investigated with 18FDG as well, but the prolactinomas could not be visualized. Three untreated patients were studied with L-[methyl-11C]methionine. The tumour-imaging potential of L-[methyl-11C]methionine and L-[1-11C]tyrosine appeared to be nearly equivalent for prolactinomas. Unlike prolactinoma tissue, the salivary glands showed a pronounced preference for L-[1-11C]tyrosine as compared to L-[methyl-11C]methionine. L-[1-11C]tyrosine is a valuable tool to obtain information on the metabolism and treatment of prolactinomas.     

Gd-EOB-DTPA-enhanced T1 relaxometry for assessment of liver function determined by real-time <Superscript>13</Superscript>C-methacetin breath test

Objectives

To determine whether liver function as determined by intravenous administration of ¹³C-methacetin and continuous real-time breath analysis can be estimated quantitatively from gadoxetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance (MR) relaxometry.

Methods

Sixty-six patients underwent a ¹³C-methacetin breath test (¹³C-MBT) for evaluation of liver function and Gd-EOB-DTPA-enhanced T1-relaxometry at 3 T. A transverse 3D VIBE sequence with an inline T1 calculation based on variable flip angles was acquired prior to (T1 pre) and 20 min post-Gd-EOB-DTPA (T1 post) administration. The reduction rate of T1 relaxation time (rrT1) and T1 relaxation velocity index (?R1) between pre- and post-contrast images was evaluated. ¹³C-MBT values were correlated with T1_post, ?R1 and rrT1, providing an MRI-based estimated ¹³C-MBT value. The interobserver reliability was assessed by determining the intraclass correlation coefficient (ICC).

Results

Stratified by three different categories of ¹³C-MBT readouts, there was a constant increase of T1 post with increasing progression of diminished liver function (p ≤ 0.030) and a constant significant decrease of ?R1 (p ≤ 0.025) and rrT1 (p < 0.018) with progression of liver damage as assessed by ¹³C-methacetin breath analysis. ICC for all T1 relaxation values and indices was excellent (> 0.88). A simple regression model showed a log-linear correlation of ¹³C-MBT values with T1_post (r = 0.57; p < 0.001), ?R1 (r = 0.59; p < 0.001) and rrT1 (r = 0.70; p < 0.001).

Conclusion

Liver function as determined using real-time ¹³C-methacetin breath analysis can be estimated quantitatively from Gd-EOB-DTPA-enhanced MR relaxometry.

Key Points

? Gd-EOB-DTPA-enhanced T1 relaxometry quantifies liver function? Gd-EOB-DTPA-enhanced MR relaxometry may provide parameters for assessing liver function before surgery? Gd-EOB-DTPA-enhanced MR relaxometry may be useful for monitoring liver disease progression? Gd-EOB-DTPA-enhanced MR relaxometry has the potential to become a novel liver function index

     

Biokinetics and radiation dosimetry for patients undergoing a glycerol tri[1-14C]oleate fat malabsorption breath test.

The glycerol tri[1-14C]olein test for fat malabsorption was carried out in two male volunteers and measurements of the loss of 14C in expired air, urine and faeces and the retention of 14C in biopsy samples of abdominal fat were made using accelerator mass spectrometry. Exhalation accounted for 73% and 55% of the administered activity and could be described by three-component exponential functions with halftimes of about 1h, 2 days and 150 days, respectively. Urinary excretion accounted for 24% of the administered activity, almost all during the first 24h after administration; about 2% was excreted in the faeces in 48h. The halftime of retention of 14C in fat ranged from 137 to 620 days. Absorbed dose calculations indicate that for a normal adult the largest dose, 1.5-7.0mGy/MBq is received by the adipose tissue, and that the effective dose is 0.3-0.5mSv/MBq. It is concluded that no restrictions need to be placed on radiation safety grounds on the administration of 0.05-0.1MBq 14C-triolein for the triolein breath test.