Shortened Survival of Fetal Erythrocytes in the Rat

Abstract

SummaryOne to 4 days before birth of their litters, pregnant buffalo rats were injected intravenously with 200 p C i of [2-I4C]glycine in order to label a cohort of fetally produced red blood cells (RBC). Shortly after birth, the newborn rats were transferred to noninjected foster mothers, and R B C survival was determined by the rate of production of 14C0 in the expired air of the newborn animals. In separate experiments, pregnant rats were injected 1-2 days before birth of their litters; blood was collected from the newborn a t 5 days of age, washed, transfused into normal adult hosts, and R B C survival determined from the resultant I4CO production. When compared with adult RBC, in situ survival of fetallv produced R B C was 2 2 % of normal (mean suggested for fetal R B C by following the rate of fall of fetal hemoglobin levels in fully compatible mothers autotransfused during the prenatal period (4,15).Recent studies of R B C destruction in the newborn dog (12) suggest a rapid elimination of fetally produced R B C during the immediate postnatal period. Since R B C survival is shorter in the premature infant than in the full term, and appears to decrease with decreasing birth weight (7). it has been concluded that R B C produced before birth have a markedly shortened survival, whereas those produced after birth have either slightly shortened or normal survival (2). The present study was undertaken in order to test this assumption by following the in situ survival of R B C produced in utero, using a noneluting cohort technique.life span of 12.1 d a i s i n the fetus, and 54.5 + 1.5 (SE) days in MATERIALS A N D METHODS the adult). This shortening of survival resulted from a n acceleration of R B C senescence (15.7 days for fetal R B C and 66.2 & 0.7 A11 studies were performed in specific pathogen-free highly days for adult RBC) and a n increased rate of random hemolysis inbred buffalo rats (Simonsen Laboratories, Gilroy, Calif.). (3.70%/day in the fetal R B C and 0.67 & 0.07%/day in adult Pregnant rats were injected intravenously with 200 p C i of [2-RBC). Although cross-transfusion of adult R B C into compatible '4C]glycine (New England Nuclear, Boston, Mass.) under light adult rat hosts resulted in only a modest shortening of R B C ether anesthesia 24-96 hr before birth of their litters. Timing of 1 lifespan (mean R B C survival reduced from 54.5 + 1.5 days to these injections was facilitated by knowledge of the time of 52.8 + 0.8 days), similar treatment of fetally produced R B C appearance of a vaginal postcoital plug. However, the variation resulted in a marked acceleration of senescence from 15.7 days in delivery times for animals with similar appearance times of t o 5.8 days. Examination of the R B C survival curves for those vaginal plugs indicated that frequent abdominal palpation and litters injected less than 7 2 hr before birth indicated the presence inspection was a more reliable indicator of impending delivery. of an additional population of cells with survival in the range of After birth of the l...

Developmental Changes in Bilirubin Production in the Rat

“…Our work shows that bilirubin production in the neonatal rat, as reflected by Veco, is elevated in a similar fashion. These results are consistent with the findings of Landaw (7), who found a markedly decreased red-cell life-span for fetal and neonatal rats with a rapid improvement in red-cell life-span during the suckling period. In contrast with the human newborn (28), the newborn rat does not exhibit a fall in absolute Veco (Veco/animal, Fig.…”

“…We have not been able to address directly the important question of the quantitative contribution of the ELP to total bilirubin production. Rather, we studied ELB in the newborn rat by determiniD& I4CO excretion following glycine-Z-v'C and 8-ALA• "CO excretion (%/30 h x )0') 0.24 ± 0.Q3 (7) p > 0.1 0.19 ± 0.015 (5) Hepatic heme oxygenase (murnol/min/Iu mg protein)…”