Evolution of NMRI Mice Ovaries and Corpora lutea during Pregnancy: Morphologic and Morphometric Study

Abstract

During pregnancy in mice, three groups of corpora lutea (CL) originating from 4 successive ovulatory cycles could be distinguished taking into account their size, cellular structure and stain affinity. Type I CL originated at the onset of pregnancy, type II CL originated during the 2 previous estrous cycles and type III CL were produced during a cycle preceding the two others. CL volume of type I increased 10-fold between day 0 and day 18.5, a 2.5-fold increase in volume occurred in type II CL between day 0 and day 3, although they derived from cycles preceding pregnancy. The volume of type III remained unchanged. This fact suggested that types I and II CL probably play a functional role in the ongoing pregnancy. After day 10 of pregnancy a high correlation coefficient (r = 0.933) is observed between type I CL and the number of embryos in the corresponding uterine horn.

Changes of Relaxin Concentrations Determined by Immunodensitometry in Ovaries of NMRI Mice during Pregnancy

“…This is however unlikely, since the same effect is observed in rather thick sections (5 pm), and furthermore, this heterogeneity re lates relatively well with the variation in the function of these cells [3]. Indeed, in our study, the amount of relaxin variabilities during pregnancy correlated well with the evolution of the size of the cell and of the nucleus [6], Furthermore, in rat luteal cells during preg nancy, a nuclear increase is also associated with the increase in cytoplasm and the metabolic activity [14].…”

“…Details concerning the upkeep, mating and sacrificing of the animals have been previously described [6]. The ovaries were fixed in Bouin-Allen fluid for 2 h at room temper ature and embedded in paraffin.…”

“…Classification of CL has been previously described [6]. Briefly, type I originates at the onset of pregnancy, type II originates during the two estrous cycles previously to the onset of pregnancy and type III originates during the cycle preceeding the two others.…”