Studies On The Source Of Progesterone During Pregnancy In Yak

This experiment was designed to study the source of progesterone during the whole gestation in yak by using radioimmunoassay(RIA) . Adrenal ,corpus luteum and placenta! tissues had been studied in 50 pregnant animals in different period of gestation. Eighteen of 50 yaks were used to detect progesterone in the media of cultured cells of the tissues, 32 in the tissue homogenate.The results showed that progesterone concentrations in the media of cultured luteum cells in vitro were gradually increasing in the first two months of gestation, (from 46.1643?1.4442ng/ml to 79.0264?.707ng/ml, P<0.05). In the following three months, namely from the 2nd to the 5th month of gestation ,the concentrations of progesterone were changing in a narrow range (from 77.3462?.6924ng/ml to 79.7495?.3470ng/ml, P>0.05).Thereafter, the concentrations increased dramatically again before the month 7.5(P<0.01). In media of cultured adrenal cells , progesteroneconcentrations were relatively low, and there were some individual differences existed within them. The levels of progesterone in the media of cultured placental cells were either very low or nondetectable.In the first 2.5 months of gestation, progesterone concentration in the tissue homogenate of copus luteum increased gradually (P<0.05),while decreased dramatically in the following 2 months (P<0.05), down to a low level of 343.7781+37.416Ing/ml at the 4th month of gestation; it increased again after the 4th month (P<0.05), reached its peak value of 586+22.996ng/ml at 6~7 month of gestation; then it decreased again. The adrenal cortical tissue homogenates had a low level of progesterone, and individual differences had been found within them. The concentrations of progesterone in placental tissue homogenate were very low or nondetectable, same as the results abtained in the media of in vitro cultured placental cells.