Lee H B, Blaufox M D
J Nucl Med. 1985 Jan;26(1):72-6.
The organ distribution of radiopharmaceuticals in the rat is usually estimated using 7% of body weight (BW) for blood volume (BV). In spite of its important impact on the evaluation of new agents, this value has not been validated adequately. We therefore studied blood volume in 70 awake Wistar rats (100 to 400 g BW) in which red blood cell volume (RBCV) and plasma volume (PV) were measured simultaneously. Red blood cell volume was measured by in vitro RBC-tagging with Tc-99m in Sn-pyrophosphate, 0.05 microgram per ml of blood; plasma volume was measured with I-125 human serum albumin (HSA). Ten minutes after injection of the dose, 0.5 ml of blood was withdrawn from the carotid or femoral artery and duplicate samples of 0.025 ml of blood were counted after separating RBCs from plasma. Total blood volume was calculated by adding RBC volume and plasma volume. The relationship for the entire group was: BV (ml) = 0.06 X BW + 0.77 (r = 0.99, n = 70, p less than 0.001). The difference between male and female rats was not statistically significant. The use of an arbitrary value of 7% for estimation of blood volume can lead to significant errors in calculating radiopharmaceutical distribution. The use of the general formula for the blood-volume calculation described here should improve the accuracy and reliability of estimates of radiopharmaceutical distribution.
放射性药物在大鼠体内的器官分布通常是使用体重（BW）的7%作为血容量（BV）来估算的。尽管这一数值对新药评估有重要影响，但其尚未得到充分验证。因此，我们对70只清醒的Wistar大鼠（体重100至400克）的血容量进行了研究，同时测量了红细胞体积（RBCV）和血浆体积（PV）。红细胞体积通过用每毫升血液含0.05微克焦磷酸锡中的Tc-99m进行体外红细胞标记来测量；血浆体积用I-125人血清白蛋白（HSA）进行测量。注射剂量10分钟后，从颈动脉或股动脉抽取0.5毫升血液，将红细胞与血浆分离后，对两份0.025毫升血液样本进行计数。总血容量通过将红细胞体积和血浆体积相加来计算。整个组的关系为：BV（毫升）=0.06×BW + 0.77（r = 0.99，n = 70，p＜0.001）。雄性和雌性大鼠之间的差异无统计学意义。使用任意7%的值来估算血容量会在计算放射性药物分布时导致显著误差。使用此处描述的血容量计算通用公式应能提高放射性药物分布估算的准确性和可靠性。
