Local control of luteal function by the uterus of the guinea-pig.

Abstract

THERE is now no doubt that distension of the uterus of a number of species of mammal results in characteristic changes in the oestrous cycle which stem from a shortening of the life span of the corpora lutea in the ovaries1,2. Thus in the guinea-pig the presence of two glass beads in each horn of the uterus, when inserted during the first four days after oestrus, shortens the length of the cycle in progress at the time of operation and that of succeeding cycles3. The degree to which the cycle is shortened appears to be governed by the number of beads in the uterus, for when one bead is present in each horn the cycle in progress is shortened from a normal length of 16 days to 14 days, whilst when two beads are present in each horn the cycle is reduced to 12 days4. Although one bead located in one horn of the uterus of the sheep exerts a definite shortening effect on the oestrous cycle5, four beads in one horn of the guinea-pig uterus do not exert as marked an effect as when they are shared between both horns. The mechanism underlying this effect is not understood, although it has been suggested that the pituitary gland is involved in exercising a luteolytic function6. The present work has been concerned with the examination of this quantitative effect at the level of the ovaries, and attention directed to the morphological changes taking place in the corpora lutea, rather than to changes in the oestrous cycle over a longer period.