Pierson R N, Wang J, Thornton J C, Van Itallie T B, Colt E W
Am J Physiol. 1984 Feb;246(2 Pt 2):F234-9. doi: 10.1152/ajprenal.1984.246.2.F234.
Four-pi whole body counting for the 1.46 meV photon of 40K has apparent advantages over single-crystal or two-pi counters in efficiency and in subject geometry independence. However, our studies of obese populations have disclosed a systematic undermeasurement of 40K, suggesting that nonhomogeneous K distribution results in systematic undercounting of 40K. In the current study 42K, emitting a 1.52 meV photon, was used in 109 volunteers ranging from 50 to 181 kg, and multiregression covariance analysis was applied to develop correction formulas based on anthropometrics. These corrections quantitatively account for the unappreciated loss of 40K and 42K photons in annular adipose tissue that surrounds the lean body, in which most K+ is concentrated. The correction ranges from 1 to 28% and is a linear (although different) function of weight in both sexes. Thus corrected, body potassium measurements, taken in conjunction with exchangeable sodium and water measurements, provide estimates for whole body osmolality that match measured serum values. Such a quantitative accounting for previously "lost" cation in 58 subjects provides independent evidence for the appropriateness and accuracy of the correction. With this correction, body potassium was recalculated in the 1,492 adult members of a previously reported group of 3,083 subjects.
用于测量⁴⁰K的1.46兆电子伏特光子的四π全身计数器在效率和与受检者几何形状无关方面比单晶或双π计数器具有明显优势。然而，我们对肥胖人群的研究发现了⁴⁰K的系统性测量不足，这表明钾分布不均导致了⁴⁰K的系统性计数不足。在当前研究中，我们使用发射1.52兆电子伏特光子的⁴²K对109名体重在50至181千克之间的志愿者进行了研究，并应用多元回归协方差分析，根据人体测量学制定校正公式。这些校正定量地考虑了在瘦体周围环形脂肪组织中未被重视的⁴⁰K和⁴²K光子损失，其中大部分K⁺集中在瘦体中。校正范围为1%至28%，并且在两性中都是体重的线性（尽管不同）函数。经过这样的校正后，结合可交换钠和水的测量结果进行的身体钾测量，可以提供与测量血清值相符的全身渗透压估计值。对58名受试者中先前“丢失”的阳离子进行的这种定量计算，为校正的适当性和准确性提供了独立证据。通过这种校正，对先前报道的3083名受试者中的1492名成年成员重新计算了身体钾含量。
