eCG는LH, FSH및 TSH와 같이 당단백질 호르몬에 속하고, 당쇄가 많이 첨가된 $alpha$와 $eta$-subunits의 비공유결합으로 구성되어 있고, 말에서 보다 다른 동물에서 FSH와 LH의 이중 생리활성을 나타내는 아주 특이한 성선 자극 호르몬이다. eCG는 임신 40~130일 사이에 말의 자궁내막배의 영양막세포에서 합성ㆍ분비된다. 따라서 본 연구에서는 eCG, eLH 및 eFSH의 각각 subunits mRNA발현을 태반과 뇌하수체에서 분석하였다. mRNA의 추출은 임신 70일의 태반과 27개월된 숫컷말의 뇌하수체에서 분리하였다. 말 태반을 이용한eCG mRNA발현의 Northern blotting분석결과 $eta$ subunit가 $alpha$ subunit보다 아주 많이 발현되었으며, 또한 뇌하수체에서 $alpha$-, LH $eta$-, FSH $eta$-subunit의 분석결과 $alpha$ subunit는 약 0.8 kb, FSH $eta$ subunit는 1.8 kb의 크기로 발현되었는데, 이러한 FSH $eta$ subunit는 cloning되어진 cDNA의 크기와 일치한다. 뇌하수체 전엽에서는 $alpha$ subunit가 LH $eta$ subunit와 FSH $eta$ subunit보다 현저히 많이 발현된다는 사실이 밝혀졌다. 따라서, 태반과 뇌하수체에서 발현되는 각각 subunit의 mRNA는 독립적으로 조절되어 결과적으로 발현량에 차이가 나타난다고 시사되어진다.
Equine chorionic gonadotropin (eCG) consists of highly glycosylated noncovalently linked $alpha$- and $eta$-subunits and belongs to the glycoprotein hormone family that includes lutropin (LH), follitropin (FSH), and thyrotropin (FSH). eCG is a unique member of the gonadotropin family because it elicits response characteristics of both FSH and LH in other species than the hone. eCG is synthesized and secreted by trophoblastic cells of the endometial cups between 40 and 130 days of gestation. In the present study, mRNA expression ratio of eCG, eLH and eFSH $alpha$- and $eta$-subunints was investigated in the placenta and pituitary. mRNA was extracted from equine placenta on day 70 of gestation and from pituitary of male horse (27 month-old). When the expression of both subunit mRNAs of eCG in the equine placenta was compared by Northern blotting, the expression of the $eta$ -subunit mRNA was relatively greater than that of the $alpha$-subunit. And mRNA expression of $alpha$-, LH $eta$- and FSH $eta$-subunits was analysed in the equine pituitary. An $alpha$-subunit was revealed with a size of approximately 0.8 kb. FSH $eta$-subunit mRNA also was detected out 1.8 kb. It is the same size of the FSH $eta$ -subunit mRNA cloned. The intensity of $alpha$-subunit mRNA was greater than that of the $eta$-subunit suggesting that the expression of $alpha$ -subunit was dominant in the equine anterior pituitary. Thus, the subunit mRNA levels seem to be independently regulated and their imbalance may account for differences in the quantities of $alpha$- and $eta$-subunits in the equine placenta and pituitary.
