title: Methodological differences account for inconsistencies in reported free VEGF concentrations in pregnant rats.
abstract: 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.
authors.affiliation: Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota; weissgerber.tracey@mayo.edu.
authors.forename: Tracey L
authors.initials: TL
authors.lastname: Weissgerber
authors.affiliation: Department of Surgery, Mayo Clinic, Rochester, Minnesota;
authors.forename: Andrea
authors.initials: A
authors.lastname: McConico
authors.affiliation: Department of Experimental Pathology and Lab Medicine, Mayo Clinic, Rochester, Minnesota;
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Knudsen
authors.affiliation: Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota;
authors.forename: Kim A
authors.initials: KA
authors.lastname: Butters
authors.affiliation: Division of Hematology, Mayo Clinic, Rochester, Minnesota;
authors.forename: Suzanne R
authors.initials: SR
authors.lastname: Hayman
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Mayo Clinic, Rochester, Minnesota;
authors.forename: Wendy M
authors.initials: WM
authors.lastname: White
authors.affiliation: Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota; Department of Biostatistics, Belgrade Medical School, Belgrade, Serbia; and.
authors.forename: Natasa
authors.initials: N
authors.lastname: Milic
authors.affiliation: Departments of Surgery, Physiology and Biomedical Engineering Mayo Clinic, Rochester, Minnesota.
authors.forename: Virginia M
authors.initials: VM
authors.lastname: Miller
authors.affiliation: Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota;
authors.forename: Vesna D
authors.initials: VD
authors.lastname: Garovic
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D051379:Mice; D011225:Pre-Eclampsia / Q000097:blood; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000097:blood*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D042461:Vascular Endothelial Growth Factor A / Q000097:blood*
chemical_list: D042461:Vascular Endothelial Growth Factor A
keywords: heparin; preeclampsia; pregnancy; sFLT-1; vascular endothelial growth factor