Shumway DA, Pavlova OA, Mukhin AG. A simplified method for the measurement of nonmetabolized 2-[18F]F-A-85380 in blood plasma using solid-phase extraction.
Nucl Med Biol 2007;
34:221-8. [PMID:
17307130 DOI:
10.1016/j.nucmedbio.2006.12.001]
[Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2006] [Revised: 11/02/2006] [Accepted: 12/05/2006] [Indexed: 11/29/2022]
Abstract
Quantification of alpha(4)beta(2)* nicotinic acetylcholine receptors using 2-[(18)F]fluoro-3-(2(S)-azetidinylmethoxy)pyridine (2-[(18)F]FA) and positron emission tomography (PET) imaging requires measurement of nonmetabolized radioligand in blood plasma, which was previously accomplished using high-performance liquid chromatography (HPLC). Here, we introduce a one-step solid-phase extraction (SPE) method for measuring the concentration of nonmetabolized 2-[(18)F]FA. This method allows many samples to be processed in a short period of time. SPE effectively separated 2-[(18)F]FA from radioactive metabolites typically observed in blood plasma after administration of radioligand in humans. Measurements of the 2-[(18)F]FA parent fraction in healthy human volunteers obtained using the SPE method were nearly identical to those obtained using HPLC (1.3+/-5% average underestimation of SPE), and reproducibility was good within and between runs (2% and 6% coefficient of variation, respectively). SPE recovery of 2-[(18)F]FA from blood plasma was not appreciably diminished (3+/-0.6%) by a larger volume of blood plasma loaded onto the cartridge, suggesting the possibility of increasing the plasma sample volume at later times in a PET study to improve measurement sensitivity. 2-[(18)F]FA was stable in blood stored on ice over 8 h and in saline at low concentrations (<2 MBq/ml) but not at high concentrations (ca. 130 MBq/ml). Using SPE, the elimination half-life and full body distribution volume of 2-[(18)F]FA in healthy human volunteers were estimated as 4.2+/-0.8 h and 220+/-70 L, respectively. These results suggest that SPE is the method of choice for the determination of the plasma 2-[(18)F]FA concentration when measurement of individual metabolites is not required.
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