Maternal dietary protein deficiency decreases nitric oxide synthase and ornithine decarboxylase activities in placenta and endometrium of pigs duringearly gestation

Little is known about the mechanism responsible for retarded placental and fetal growth induced by maternal dietary protein malnutrition. On the basis of the recent finding that nitric oxide (NO) and polyamines (products of L -arginine) play an important role in embryonic and placental development, t he present study was designed to determine whether protein deficiency decre ases placental and endometrial activities of NO synthase (NOS) and ornithin e decarboxylase (ODC) (the first and key regulatory enzyme in polyamine syn thesis). Primiparous gilts selected genetically for low or high plasma tota l cholesterol concentrations (low line and high line, respectively) were ma ted and then fed 1.8 kg/d of isocaloric diets containing 13% or 0.5% crude protein. At d 40 or 60 of gestation, they were hysterectomized, and placent a and endometrium were obtained for incubations, NOS and ODC assays, and me asurements of free amino acids and polyamines, Maternal dietary protein res triction decreased arginine and ornithine concentrations, constitutive and inducible NOS activities and NO production, as well as ODC activity and pol yamine concentrations in placenta and endometrium of both lines of gilts. P lacental NO synthase activity and NO generation were lower in high line gil ts than in low line gilts, ODC activities and polyamine concentrations in p lacenta and endometrium were decreased at d 60 compared with d 40 of gestat ion, These changes in placental and endometrial synthesis of NO and polyami nes during early gestation may be a mechanism responsible for reduced place ntal and fetal growth in protein-deficient gilts and for altered conceptus development in high line gilts.