Effects of a superovulatory dose of pregnant mare’s serum gonadotropin on uterine morphology, carbohydrate histochemistry and serum steroids in immature rates
Creators: name: Nehr, Sonja I.
Publisher: name: University of British Columbia
Year: 2008

description: Infertility, defined as the failure to conceive or induce conception, is a common and serious problem in both humans and domestic livestock. Superovulation with exogenous gonadotropins in conjunction with in vitro fertilization and embryo transfer is one method used to treat this problem. However, superovulation is associated with a decreased pregnancy rate. The objective of this research was to determine whether this decreased fertility rate was associated with changes in the uterus. This study compared the effects of a superovulatory (40 IU) and a physiological (4 IU) dose of pregnant mare's serum gonadotropin (PMSG) on the morphology of the endometrium and the carbohydrate composition of the uterine glycocalyx and secretions in immature rats and in untreated mature rats. The morphological and carbohydrate histochemical changes found were correlated to the serum concentrations of estradiol, progesterone and androgens. Female 28 day old Sprague-Dawley rats were injected with PMSG (4 or 40 IU,subcutaneous). Subgroups of rats (n = 6 /dose) were sacrificed immediately before injection and at 24 h intervals for 9 days after initial treatment (total n = 114). Serial 4 micron thick paraplast sections of Bouin's fixed uteri were stained with hematoxylin and eosin formorphological assessment. A battery of histochemical staining methods selective for sulphate esters, sialic acid, neutral sugars and glycogen were used for assessing the carbohydrate composition of the uterine secretions and the glycocalyx. Serum estradiol, progesterone and androgen concentrations were determined by radioimmunoassay. The morphology of the endometrium, the amount and carbohydrate composition of the uterine secretions and glycocalyx as well as the steroid patterns in the 4 IU PMSG treatedrats were similar to that seen in the mature rats. In the 40 IU PMSG group, the morphological changes of the endometrium include hyperplasia, disorganization of the subepithelial stroma and an increase in the length of the internal lumen perimeter. This superovulatory group had an increase in the amount of the uterine secretions and glycocalyxwhen compared to the mature and 4 IU PMSG group (p&lt;0.001). The secretions within the superovulatory group showed increases in the amount of sialic acid and neutral sugars present, while the glycocalyx showed increases in only neutral sugars when compared to the mature and 4 IU PMSG group (p&lt;0.001). The serum concentrations of estradiol, progesterone and androgens were higher in the superovulatory group (p&lt;0.05) and the morphological and histochemical changes found in the uteri of superovulated rats may be caused by these prolonged and increased estradiol and progesterone concentrations. These morphological and endometrial changes may result in a uterus that is no longer suitable for proper blastocyst-endometrial interaction and therefore prevent successful implantation in the superovulatedrat.