TEMPORAL CHANGES TO UTERINE COLLAGEN TYPE-I, TYPE-III AND TYPE-V IN RELATION TO EARLY-PREGNANCY IN THE RAT

Uterine tissues of pregnant rats were extracted to define any changes to the proportions of collagens types I, III and V. The total concentr ation of extracted collagen was determined in tissue samples from impl ant and adjacent non-implant (NI) sites. Extracts were also subjected to polyacrylamide gel electrophoresis (PAGE), immunoblotting and gel d ensitometry to define the collagen types and to determine their relati ve proportions. By relating the proportions to the collagen concentrat ions in the extracts, type I was found to be the predominant collagen in both tissue regions although the concentration in the implant sites was lower than that in the NI sites. The concentration of Type I coll agen decreased significantly over the period of observation in both im plant and NI sites. Although the concentrations of collagen type III a nd type V also decreased in the implant sites, they did not alter in t he NI sites. The results demonstrate that shortly after the initiation of implantation the uterus responds to the presence of the implanting embryo by decreasing the concentration of all three types of collagen . This indicates that their metabolism may, in part, be regulated by s imilar mechanisms. Furthermore, it was evident that a decrease in the concentration of collagen type I was initiated in uterine areas that, at the time of sampling, were not directly involved with implantation. During the study, it was found that the alpha(1) chain of collagen ty pe V separated into two distinct bands when run on gels containing 3.8 M urea. When purified uterine type V collagen was subjected to PAGE w ith increasing concentrations of urea in the separating gels, there wa s a noticeable change in the migration of this particular chain.