Maternal lung growth in surgically reduced litter size pregnancy

In our previous study (Faridy et al., this issue) we observed that pregnant rats with large litter size have larger lungs than rats with small litter size. The present study was conducted to test the hypothesis that in large litter size pregnancy, the maternal lung may not enlarge if, during pregnancy, the large litter size of 11-18 is surgically reduced to a small litter size of 3. A laparotomy was performed in pregnant albino rats at gestation day 7 (R7) or 14 (R14), all fetuses except 3 were removed and the rats were sacrificed at gestation day 21 (term 22 days). Maternal lung growth was assessed by measuring lung weight, lung DNA content and lung air volume, and the fetal lung growth by lung DNA content. The results were then compared with control pregnant rats of large (11-18) and small (1-3) litter size. The findings were: (1) reduction of litter size hindered maternal lung enlargement; (2) the earlier in pregnancy the surgical reduction was performed the smaller was the maternal lung, such that control (11-18) greater than R14 greater than R7 = control (1-3); (3) fetuses of R14 rats had larger lungs per body weight than R7 rats; (4) oxygen consumption of sham-operated rats with large litter size was higher (by 8-12%) than R7 rats. The results suggest that enlargement of maternal lung during pregnancy is related to litter size and perhaps to VO2. The fact that R14 fetal lung is larger than that of R7, supports our previous notion (Faridy et al., this tissue) that factors regulating the maternal lung growth similarly influence the fetal lung.