Plasminogen activator activity and plasminogen activator inhibition in the uterus of ewes after the induction of oestrus synchronization or superovulation, involving eCG

Abstract

During the preimplantation period, early mammalian embryos largely depend on uterine environment. Concurrently, uterine architecture undergoes substantial growth and remodeling under the influence of ovarian steroids. Plasminogen activators/plasmin proteolytic system that is implicated in tissue remodeling is affected by reproductive hormone variations. Thus, hormone treatments for reproductive function control possibly influence proteolytic enzyme activity in the reproductive tract and its study in uterine fluid and endometrium could demonstrate possible changes in uterine environment. This work examines (a) the effect of hormone treatment involving eCG in the dosage used for oestrus synchronization or for superovulation on plasminogen activator activity (PAA) and plasminogen activator inhibition (PAI) in the uterus of ewes before maternal recognition of pregnancy and (b) the possible relationships among blood ovarian steroid concentration, proteolytic enzyme activity and ovarian response/embryo yield. Chios ewes (n = 24) were treated with progestagen intravaginal sponges for 12 days and eCG (500 or 1000 IU) at sponge removal; ewes at the second oestrus after synchronization were used as controls. On day 6 of the oestrous cycle, after slaughter, ovarian response was assessed and embryos were collected; uterine horn flushings (UHF), caruncular endometrium (CE) and intercaruncular (ICE) endometrium samples were collected, for PAA and PAI photometrical assessment. Oestradiol-17β (E2) and progesterone (P4) concentration was assessed in blood serum samples collected before slaughter by a radioimmunoassay. A significant increase of PAA in the UHF was observed after treatment; PAA in UHF was significantly associated with the number of embryos or high-quality embryos, while PAA in UHF per embryo or high-quality embryo was not affected by treatment. No significant effect of treatment was noticed on PAA or PAI in the endometrium (CE, ICE). In UHF and in ICE, PAI against tissue-type PA had a significant positive relationship with PAI against urokinase-type PA. PAI against tissue-type PA in CE had significant negative relationship with E2 concentration. In conclusion, hormone treatment involving eCG in the dosage used for superovulation and, to a lesser degree, in the dosage used for oestrus synchronization affected PAA in the uterus of Chios ewes, before maternal recognition of pregnancy, but did not seem to disturb reproductive function.