Effect of gestational age and fetal sex on metabolism of creatine by uteri, placentae, and fetuses of pigs

Abstract The creatine (Cr) biosynthesis pathway buffers ATP in metabolically active tissues. We investigated whether sex of fetus and day of gestation influence Cr in endometrial and conceptus tissues from gilts on Days 60 and Day 90 (n = 6 gilts/day) of gestation. Uterine and conceptus tissues associated with one male and one female fetus from each gilt were analyzed for creatine, mRNAs, and proteins for Cr biosynthesis. Total Cr decreased in amniotic fluid but increased in allantoic fluid between Days 60 and 90 of gestation for male (P < 0.05), but not for female fetuses (P > 0.05). Endometrial expression of CKM, CKMT1, and SLC6A8 mRNAs increased (P < 0.05) between Days 60 and 90 only for female fetuses. On Day 60, expression of CKB and CKMT1 mRNAs was greater (P < 0.05) for placentae of female than male fetuses. Livers of male fetuses had greater expression of AGAT and CKB than for females on Day 60, while kidneys of female fetuses had greater expression of GAMT than male fetuses on Day 90 (P < 0.05). Localization of GAMT, CKB, CKMT1 and SLC6A8 proteins to uterine and chorionic epithelium was not influenced by gestational age or fetal sex. AGAT localized to fetal kidneys and appeared greater on Day 90 than Day 60 in both sexes. Thus, expression of the creatine-creatine kinase-phosphocreatine (Cr-CK-PCr) system at the uterine-conceptus interface is affected by gestational age and fetal sex to influence energy homeostasis in pigs.