Blood volume in the pregnant rabbit

Red cell and plasma volumes were measured using 51Cr-labelled red cells and 125I-labelled HSA respectively, in seventeen pregnant rabbits at 28-29 days of pregnancy, and fifteen non-pregnant rabbits weight-matched with the pregnancy rabbits before mating. Red cell volume in the pregnant group (20.0 +/- 2.8 ml . kg-1; mean +/- S.D.), was greater than in the control rabbits (18.0 +/- 2.0 ml . kg-1; P less than 0.05); plasma volumes (39.0 +/- 4.5 and 37.3 +/- 4.4 ml . kg-1 respectively) were not statistically different. Blood volume was derived from the sum of independently measured red cell and plasma volumes. That of the pregnant group (59.0 +/- 5.3 ml . kg-1) was just significantly greater than that of control rabbits (55.3 +/- 5.3 ml . kg-1; P less than 0.05). When the volume of distribution of the labels was corrected, by subtracting fetal weight from maternal body weight, the red cell, plasma and blood volumes were all significantly greater in the pregnant rabbits (P less than 0.02). Although the large vessel haematocrit of the pregnant group (41.6 +/- 4.4%) exceeded that of the non-pregnant group (38.7 +/- 2.6%; P less than 0.05), there was no significant difference in whole body haematocrit or Fcells (the ratio of the whole body to large vessel haematocrit) between the two group of rabbits.