Effects of oxytocin treatment early in pregnancy on fetal growth in ad libitum-fed and food-restricted rats.
The effects of oxytocin on fetal and placental growth and on maternal weight gain and accumulation of body fat were studied in ad libitum-fed and food-restricted (receiving 70% of the food intake of the ad libitum-fed group) pregnant rats. Further, a possible role of the IGF axis in mediating oxytocin-induced changes was assessed. Pregnant rats were injected subcutaneously once a day during gestational d 1-5 with saline or oxytocin (1 mg/kg). Ad libitum-fed oxytocin-treated pregnant rats had higher circulating levels of IGF-I, larger placentas, fetuses, and newborn pups and contained less body fat at the end of pregnancy. In food-restricted dams, oxytocin-treatment had no effect on fetal and placental growth. Additionally, food restriction attenuated the normal increase in IGF binding protein-3 protease proteolysis during pregnancy. The results show that oxytocin may affect maternal adaptations to pregnancy and stimulate fetal growth. We suggest that this effect may be mediated by increased IGF-I in ad libitum-fed animals, whereas food restriction may block this effect by resulting in low levels of circulating IGF-I and by attenuating the pregnancy-associated increase in IGF binding protein-3 protease activity and, thereby, further compromise IGF bioavailability.
Sohlström
A
A
Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
Carlsson-Skwirut
C
C
Bang
P
P
Brismar
K
K
Uvnäs-Moberg
K
K
D000273:Adipose Tissue / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001835:Body Weight; D004435:Eating; D005314:Embryonic and Fetal Development / Q000187:drug effects* / Q000502:physiology; D005260:Female; D005508:Food Deprivation / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000502:physiology*; D010121:Oxytocin / Q000494:pharmacology*; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley
D010121:Oxytocin; D007334:Insulin-Like Growth Factor I