title: Timing of fetal nucleated red blood cell count elevation in response to acute hypoxia.
abstract: We determined the effect of an acute episode of severe hypoxia on peripheral nucleated red blood cell (RBC) counts in the fetal rat. Timed pregnant rats were randomized to a 2-hour exposure to hypoxia (placement in a chamber containing a gas mixture with 9% O2 +3% CO2 + balanced N2) or to a 2-hour exposure to a sham chamber containing room air. Two maternal animals per group underwent cesarean section immediately after the 2-hour period and then 4, 12, 24, 36, 48, and 60 h after exposure. Fetal nucleated RBC counts were compared between groups at each time interval. The nucleated RBC counts were not significantly different in the hypoxia group until 12 h (mean +/- SEM 158.0 +/- 22.4 RBC/10 high-power fields vs. 90.6 +/- 11.0; p = 0.03) and 24 h (133.2 +/- 16.0 vs. 84.1 +/- 9.0; p = 0.04) after exposure. There were no differences between groups 36, 48, and 60 h after exposure. In the near-term rat fetus, acute hypoxia was associated with a delayed but transient increase in peripheral nucleated RBC counts.
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Wayne State University, Detroit, MI 48201, USA. sblackwe@med.wayne.edu
authors.forename: Sean C
authors.initials: SC
authors.lastname: Blackwell
authors.forename: Mordechai
authors.initials: M
authors.lastname: Hallak
authors.forename: John W
authors.initials: JW
authors.lastname: Hotra
authors.forename: Jerrie
authors.initials: J
authors.lastname: Refuerzo
authors.forename: Sonia S
authors.initials: SS
authors.lastname: Hassan
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Sokol
authors.forename: Yoram
authors.initials: Y
authors.lastname: Sorokin
mesh_terms: D000818:Animals; D004900:Erythroblasts / Q000166:cytology*; D004906:Erythrocyte Count; D005260:Female; D005312:Fetal Blood / Q000166:cytology*; D005311:Fetal Hypoxia / Q000097:blood*; D011247:Pregnancy; D051381:Rats; D020318:Rats, Long-Evans; D013997:Time Factors