Identification of Retinol-binding Protein Produced by Caprine Endometrium during Periattachment Period of Early Pregnancy

K H Liu ,Jian‐Jia Huang ,Jing Lin

doi:10.5713/ajas.2002.1708

Abstract

Endometrial explants obtained from does between days 13 and 21 of pregnancy were cultured in a modified minimum essential medium in the presence of ( 35 S)methionine and ( 3 H)-leucine. Proteins synthesized and secreted into medium were analyzed by fluorography of two-dimensional polyacrylamide gel electrophoresis and fluorography. No marked qualitative changes in patterns of protein production by caprine endometrium between days 13-21 of pregnancy. At least 11 proteins showed consistently a clear spot or a grouping of spots with characteristic location on two-dimensional gels. A major low molecular weight protein consisted of two major isoforms (pI 5.3-6.0) of similar molecular mass (21 kDa). Limited N-terminal sequence analysis of these two isoforms showed that the protein had complete homology with bovine placental and plasma retinol-binding protein (RBP) over the first 20 amino acids. Through use of the antiserum raised against bovine placental RBP, immunoreactive RBP was detected in cultures conditioned by uterine explants prepared at days 13, 15 and 21 of pregnancy. In the present study, proteins synthesized and secreted by caprine endometrium during periattachment period of early pregnancy were characterized. The pregnant endometrium secreted a number of neutral-to-acidic proteins which constituted, in part, the histotroph. A vitamin A-transport protein, RBP, was identified in cultures conditioned by endometrium of days 13-21 of pregnancy. The uterine endometrium is the only source of retinol for embryonic tissues. The uterine RBP appears to transport retinol locally toward embryonic tissues. Secretion of RBP by caprine endometrium of days 13, 15 and 21 of pregnancy suggested that retinol played an important role in conceptus development during periattachment period of early pregnancy. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 12 : 1708-1713)

Highlights

In caprine, the period of placentation of conceptus to the uterine endometrium is relatively late
The array of polypeptides synthesized and secreted by caprine endometrium between days 13-21 of pregnancy were characterized by 2D-polyacrylamide gel electrophoresis (PAGE)
Pregnant uterus was the source of a number caprine endometrium was active in protein synthesis and of neutral-to-acidic proteins, which constituted, in part, the histotroph

Summary

Introduction

The period of placentation of conceptus to the uterine endometrium is relatively late. Adhesion of trophoblast and uterine epithelium occurs between day 19 and 23 after mating (Wongo et al, 1990). During this time period, uterine secretions, called histotroph, are important to provide nourishment for the embryo. Uterine secretions may be associated with maternal-fetal interactions. The phenomenon, known as maternal recognition of pregnancy occurs between days 15-17 of pregnancy in goats (Gnatek et al., 1989). Several low molecular weight proteins secreted by caprine endometrium have been suggested to be involved in the process of maternal recognition of pregnancy (Weise et al, 1993)

Methods

Results

Conclusion