Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota;
Department of Surgery, Mayo Clinic, Rochester, Minnesota;
Am J Physiol Regul Integr Comp Physiol. 2014 Jun 1;306(11):R796-803. doi: 10.1152/ajpregu.00544.2013. Epub 2014 Mar 12.
Free vascular endothelial growth factor (VEGF) is undetectable in plasma during human pregnancy. However, studies examining pregnant rats have reported both low (8-29 pg/ml) and high (527-1,030 pg/ml) free VEGF. These discrepancies cast uncertainty over the use of rat models to study angiogenic factors in pregnancy and preeclampsia. This study investigates methodological factors that may explain these discrepancies. Plasma VEGF in nonpregnant, day 7 pregnant, and day 19 pregnant rats was measured using rat and mouse ELISAs (R&D Systems). The rat ELISA detected VEGF in plasma from nonpregnant rats but not in plasma from day 19 pregnant rats. The mouse ELISA detected higher VEGF concentrations than the rat ELISA in every sample tested. This discrepancy was greater in day 19 pregnant rats (median: 2,273 vs. 0 pg/ml) than in nonpregnant (97 vs. 20 pg/ml) and day 7 pregnant (66 vs. 2 pg/ml) rats. Recovery of recombinant rat VEGF (rrVEGF) spiked into plasma from nonpregnant and day 7 pregnant rats was high for the rat ELISA (82-105%) but low for the mouse ELISA (17-22%). The rat ELISA did not recover rrVEGF in plasma from day 19 pregnant rats, suggesting that this ELISA measures free VEGF. The use of the rat versus mouse ELISA likely explains the differences in reported VEGF concentrations in pregnant rats. While the rat ELISA appears to measure free VEGF, plasma concentrations in nonpregnant and pregnant rats are below the assay sensitivity limit. As most previous studies of pregnant rats used the mouse VEGF ELISA, these data should be interpreted cautiously.
在人类妊娠期间，血浆中无法检测到游离血管内皮生长因子 (VEGF)。然而，研究检查怀孕大鼠时，报告了低水平（8-29 pg/ml）和高水平（527-1030 pg/ml）的游离 VEGF。这些差异使得使用大鼠模型来研究妊娠和子痫前期中的血管生成因子的应用存在不确定性。本研究调查了可能解释这些差异的方法学因素。使用大鼠和小鼠 ELISA（R&D Systems）检测非妊娠、妊娠第 7 天和妊娠第 19 天大鼠的血浆 VEGF。大鼠 ELISA 可检测非妊娠大鼠血浆中的 VEGF，但不能检测妊娠第 19 天大鼠血浆中的 VEGF。在每个测试样本中，小鼠 ELISA 检测到的 VEGF 浓度均高于大鼠 ELISA。在妊娠第 19 天大鼠（中位数：2273 与 0 pg/ml）中，这种差异大于非妊娠（97 与 20 pg/ml）和妊娠第 7 天大鼠（66 与 2 pg/ml）。对于大鼠 ELISA，添加到非妊娠和妊娠第 7 天大鼠血浆中的重组大鼠 VEGF（rrVEGF）回收率很高（82-105%），但对于小鼠 ELISA 回收率很低（17-22%）。大鼠 ELISA 无法从妊娠第 19 天大鼠的血浆中回收 rrVEGF，这表明该 ELISA 测量游离 VEGF。使用大鼠 ELISA 而非小鼠 ELISA 可能解释了报道的妊娠大鼠 VEGF 浓度的差异。虽然大鼠 ELISA 似乎测量游离 VEGF，但非妊娠和妊娠大鼠的血浆浓度低于检测灵敏度极限。由于大多数先前的妊娠大鼠研究使用小鼠 VEGF ELISA，因此应谨慎解释这些数据。
