AJP - Regulatory, Integrative and Comparative Physiology, Vol 265, Issue 2 399-R403, Copyright © 1993 by American Physiological Society
Serum immunoreactive erythropoietin and red blood cell mass during pregnancy in conscious rats
G. O. Del Valle, M. D. Mosher and K. P. Conrad
Department of Physiology, University of New Mexico School of Medicine, Albuquerque 87131.
Serum erythropoietin concentration increases during human pregnancy and
presumably accounts for expansion of red blood cell mass. The mechanism(s)
underlying gestational changes of serum erythropoietin are unknown.
Moreover, if erythropoietin synthesis increases, then the organ(s)
questions about erythropoietin in pregnancy, we first set out to establish
an animal model. Chronically instrumented, conscious unrestrained rats were
studied. 51Cr-labeled red blood cells and radioimmunoassay were used to
assess red blood cell mass and serum erythropoietin, respectively. Except
for a lower hematocrit (P < 0.05 vs. virgin rats) and a slightly higher
plasma volume (P value not significant) for gravid rats on gestational day
6, all other variables measured in early pregnancy rats were comparable to
those measured in virgin control animals. Significant increases in total
blood volume, plasma volume, and red blood cell mass were observed by
gestational day 13 (midpregnancy) when compared with virgin control rats.
These changes were even more pronounced on gestational day 20. Serum
immunoreactive erythropoietin was also significantly increased at both of
these stages of pregnancy. We conclude that the gravid rat is a reliable
animal model of human gestation in which to further investigate
erythropoietin in pregnancy.
