Uterine and oviductal samples were collected from twenty two primiparous
sows on their second estrus following weaning. Based on the timing of
ovulation determined by real-time ultrasound, samples were collected from a
minimum of three sows whose temporal reproductive status corresponded to
the germinal vesicle (GV) and metaphase two (MII) stages of oocyte
maturation, and the 2-cell, 4-cell, early morula (8- to 16-cell), morula and
blastocyst stages of embryonic development. Each uterine horn was divided
into three equal length sections by ligature to represent the lower- (cervical),
mid- and upper (oviductal) sections of the horn. Warm PBS was then used to
flush each oviduct (5ml) and each section of the uterine horns (20 m).
Hyaluronic acid concentrations in flushings were determined using an HA
specific ELISA (Hyaluronan Duo Set, R&D systems) and the volume of each
flush was used to estimate total HA content (ng per flush). No differences
(P>0.05) in HA content were found between uterine sections at any stage of
gestation. HA content of uterine flushings decreased (P<0.0001) between the GV and 2-cell stages, and then steadily increased (P<0.001-0.01) through the morula and blastocyst stages of development.