Clerico A, Iervasi G, Berti S, Pilo A, Vitek F, Salvadori S, Marastoni M, Manfredi C, Del Chicca M G, Iascone M R
Instituto di Fisiologia Clinica del CNR, Pisa, Italy.
J Endocrinol Invest. 1995 Mar;18(3):194-204. doi: 10.1007/BF03347802.
Using a tracer method, we evaluated, in vivo, the main turnover parameters and the main metabolic pathways of ANP in 10 normal subjects. HPLC was used to purify the labeled hormone and the principal labeled metabolites present in venous plasma samples collected at determined times after tracer injection. The main ANP kinetic parameters were derived from the disappearance curves of [125I] ANP, which were satisfactorily fitted by a biexponential function in all subjects. Newly produced ANP initially distributes in a large, plasma equivalent space (10.9 +/- 3.6 l/m2 body surface); the hormone rapidly leaves this space due to both degradation and to distribution in peripheral spaces. The mean residence time in the body (19.4 +/- 19.8 min) and the plasma equivalent total distribution volume (28.2 +/- 11.5 l/m2) indicate that ANP is also widely distributed outside the initial space in humans (circulating ANP is no more than 1/15 of the body pool). Metabolic clearance rate values were distributed across a wide range (from 740 ml/min/m2 to 2581 ml/min/m2, mean 1849 ml/min/m2), and were shown to strongly correlate (R = 0.962) with the daily urinary excretion of sodium. A complete separation of labeled ANP from its labeled metabolites was achieved by the HPLC technique; at least 3 different peaks due to labeled metabolites in vivo produced from the injected [125I]ANP1-28 were found. The first chromatographic peak eluted showed an identical elution time to monoiodotyrosine. At least two other peaks due to in vivo generated labeled metabolites were well identified in the chromatograms: one peak (coeluting with labeled COOH-terminal tripeptide, H-Phe-Arg-Tyr-OH) was eluted ahead and one (coeluting with labeled peptide fragments ANP7-28, ANP13-28, and ANP18-28) behind the elution peak of the labeled ANP. The peak of labeled tyrosine appearing in the plasma ranged between 3 and 5 min after tracer injection; the other two peaks of radioiodinated metabolites showed their highest activity in the first sample (1.5 min), suggesting an earlier occurrence of their peaks. These labeled metabolites seem to be intermediate peptides, between the intact circulating form of the hormone and the final labeled metabolite (tyrosine), which is the last amino acid of the peptide hormone, produced in vivo after injection of the tracer.(ABSTRACT TRUNCATED AT 400 WORDS)
我们采用示踪法在10名正常受试者体内评估了心钠素（ANP）的主要周转参数和主要代谢途径。利用高效液相色谱法（HPLC）纯化示踪剂注射后在特定时间采集的静脉血浆样本中存在的标记激素和主要标记代谢物。主要的心钠素动力学参数源自[125I]ANP的消失曲线，所有受试者的该曲线均能很好地用双指数函数拟合。新产生的心钠素最初分布于一个较大的、相当于血浆的空间（10.9±3.6升/平方米体表面积）；由于降解和向周围空间的分布，该激素迅速离开这个空间。在体内的平均停留时间（19.4±19.8分钟）和相当于血浆的总分布容积（28.2±11.5升/平方米）表明，心钠素在人体内也广泛分布于初始空间之外（循环中的心钠素不超过体内总量的1/15）。代谢清除率值分布范围很广（从740毫升/分钟/平方米至2581毫升/分钟/平方米，平均为1849毫升/分钟/平方米），并且显示出与每日尿钠排泄量密切相关（R = 0.962）。通过HPLC技术实现了标记的心钠素与其标记代谢物的完全分离；在体内由注射的[125I]ANP1 - 28产生的标记代谢物至少发现了3个不同的峰。洗脱的第一个色谱峰显示出与单碘酪氨酸相同的洗脱时间。在色谱图中还很好地鉴定出至少另外两个由于体内产生的标记代谢物形成的峰：一个峰（与标记的COOH末端三肽H - Phe - Arg - Tyr - OH共洗脱）在标记的心钠素洗脱峰之前洗脱，另一个峰（与标记的肽片段ANP7 - 28、ANP13 - 28和ANP18 - 28共洗脱）在标记的心钠素洗脱峰之后洗脱。示踪剂注射后3至5分钟血浆中出现标记酪氨酸的峰；另外两个放射性碘化代谢物的峰在第一个样本（1.5分钟）时活性最高，表明它们的峰出现得更早。这些标记代谢物似乎是中间肽，介于激素的完整循环形式和最终标记代谢物（酪氨酸）之间，酪氨酸是肽激素的最后一个氨基酸，在注射示踪剂后在体内产生。（摘要截选至400字）
