M. Hirako et al., Oestrone sulfate commences an increase around 50 days of gestation in bovine peripheral blood, REPROD FERT, 12(7-8), 2000, pp. 351-354
The objective of this study was to determine the peripheral plasma concentr
ation of oestrone sulfate during early gestation in the cow with a sensitiv
e assay system. Five Holstein heifers were inseminated on oestrus and bled
from the jugular vein at regular intervals until 100 days of gestation. Oes
trone sulfate, oestrone and oestradiol-17 beta in blood plasma were extract
ed with a reverse-phase cartridge and each measured by specific radioimmuno
assay. Oestrone sulfate in bovine circulation started to increase around 50
days of gestation. whereas oestrone and oestradiol-17 beta remained at bas
al concentrations for 80 days. The plasma concentration of oestrone sulfate
increased gradually and linearly from 50 days of gestation, and was drasti
cally elevated after 80 days of gestation before the increase in unconjugat
ed oestrogens. The rate of increase from 80 to 100 days was the greatest fo
r oestrone sulfate concentration among all oestrogens. These results sugges
t that plasma oestrone sulfate concentration could be a useful indicator of
pregnancy within the first trimester of gestation in the cow.