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A Comparative Study of Ovine Placental Lactogen and Prolactin Secretion Patterns in Genetically Dissimilar Fetal Co-Twins¹

University of California, Davis 95616

⁵ To whom reprint requests should be addressed.

Abstract

Simultaneous fetal and maternal ovine placental lactogen (oPL) and prolactin (oPRL) measurements were determined from blood samples collected from six mixed breed (MB; gestation = 141.5 ± .7 d) pregnancies and single Rambouillet (n = 2; Ra gestation = 148 and 149 d) and Finnish Landrace (n = 2; Finn gestation = 141 and 143 d) pregnancies for the purpose of examining a possible relationship between fetal-maternal oPL and oPRL levels in the prepartal period. The MB pregnancies were produced by embryo transfer and consisted of genetically different fetuses co-existing in a common uterine environment. Despite the apparent prematurity of Ra co-twins in MB pregnancies, similar oPL and oPRL patterns during the final 14 d of gestation were observed for both Ra and Finn co-twins. Fetal oPL levels decreased at parturition (range 23 to 90 ng/ml) to approximately 60% of values recorded 8 d prepartum (range 100 to 150 ng/ml) in both fetal siblings. Increases in fetal oPRL concentrations, first observed at approximately 4 d prepartum in all fetuses, reached peak concentrations (40 to 60 ng/ml) at term. Results of this study suggest a similarity in regulation of fetal oPL and oPRL secretion, despite genetic differences for gestation period, in fetuses in the M.B. pregnancy.

The authors thank the members of the embryo transfer team for their assistance with surgeries and Mark Starr for his assistance with the prolactin assays. DDK was supported by a Natural Sciences and Engineering Research Council of Canada Postdoctoral Fellowship. Portions of the research were also supported by funds from the W-112 Western Regional Research Project (GBA), the California Agricultural Experiment Station, Steroid Metabolism in Domestic Animals (GHS) and NIH grant HD-07447 (SH).

² Present address: Dept. of Food Sci., Univ. of British Columbia, B. C, Canada.

³ Dept. of Anim. Sci.

⁴ Dept. of Reprod.

⁶ Dept. of Pediatrics, Duke Univ. Medical Center, Durham, NC 27710.