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Excess estrogen sulfoconjugation as the possible cause for a poor sign of parturition in pregnant cows carrying somatic cell clone fetuses

H Hirayama, Hokkaido Animal Research Center, Hokkaido, Japan
K Sawai, Department of Animal Science, Faculty of Agriculture, Iwate University, Iwate, Japan
S Moriyasu, Hokkaido Animal Research Center, Hokkaido, Japan
M Hirayama, National Livestock Breeding Center Tokachi Station, Hokkaido, Japan
Y Goto, National Livestock Breeding Center Tokachi Station, Hokkaido, Japan
E Kaneko, Graduate School of Animal and Food Hygiene, Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, Japan
A Miyamoto, Graduate School of Animal and Food Hygiene, Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, Japan
K Ushizawa, Reproductive Biology Research Unit, Division of Animal Science, National Institute of Agrobiological Sciences, Ibaraki, Japan
T Takahashi, Reproductive Biology Research Unit, Division of Animal Science, National Institute of Agrobiological Sciences, Ibaraki, Japan
A Minamihashi, Hokkaido Konsen Agricultural Experiment Station, Hokkaido, Japan

Correspondence: Hiroki Hirayama, Email: h.hirayama{at}agri.pref.hokkaido.jp

Abstract

We conducted this study to elucidate a factor causing a poor sign of parturition and prolonged gestation, which are frequently observed in cows carrying somatic clone fetuses. Prepartum rises in concentrations of plasma estrone and estradiol-17β in the recipient cows pregnant with clones were subtle. In contrast, plasma concentration of estrone sulfate in clone pregnancies increased gradually from pre-initiation of parturition induction whereas control cows which received in vivo-derived embryos showed a significant increase at parturition. Therefore, in clone pregnancies, the ratio of estrone/estrone-sulfate was low during prepartum period compared with control. Messenger RNA expression of estrogen sulfotransferase (SULT1E1) in the placenta at parturition was significantly higher in clone pregnancies than control pregnancies, and was localized in binucleate cells. SULT1E1 mRNA abundance was negatively and positively correlated with concentrations of maternal estrone and estrone sulfate at parturition, respectively. Messenger RNA expressions of estrogen sulfatase (STS) and aromatase (CYP19) were similar between clone and control pregnancies, and were localized in binucleate cells and carunclar epithelial cells. STS and CYP19 mRNA abundances showed positive correlations with maternal estradiol-17β concentration. The population of binucleate cells in the placenta did not differ between clone and control pregnancies. Plasma cortisol concentration of vaginally delivered newborn clone calves was comparable to those of control, although cesarean section delivered clone calves showed a low concentration. These results suggest that excess estrogen sulfoconjugation is the reason for the perturbed low ratio of active to inactive estrogens and the resulting hormonal imbalance contributes to the lack of overt signs of readiness for parturition in cows pregnant with clones.