Temporal changes to uterine collagen types I, III and 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 concentration of extracted collagen was determined in tissue samples from implant and adjacent non-implant (NI) sites. Extracts were also subjected to polyacrylamide gel electrophoresis (PAGE), immunoblotting and gel densitometry to define the collagen types and to determine their relative proportions. By relating the proportions to the collagen concentrations 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 collagen decreased significantly over the period of observation in both implant and NI sites. Although the concentrations of collagen type III and type V also decreased in the implant sites, they did not alter in the 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 similar 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 type V separated into two distinct bands when run on gels containing 3.8 M urea.(ABSTRACT TRUNCATED AT 250 WORDS)