The effects of prostaglandin F2alpha on the fine structure of the corpus luteum of the pregnant hamster.

Corpora lutea (C.L.) from normal and prostaglandin-treated pregnant hamsters were examined by light and electron microscopy. Luteal cells from pregnant control animals were hypertrophied and contained an abundance of agranular endoplasmic reticulum (AER) suggesting steroidogenic activity. Animals which were injected on day 4 of pregnancy had ovulated by the third day following the injection, hence, two generations of corpora lutea were present in the ovary. Luteal cells from the "old" C.L. of pregnancy underwent a progressive degeneration during the four days following the single prostaglandin injection, whereas, cells from "new" C.L. appeared viable in most respects. The presence of aggregated platelets in both "old" and "new" C.L. was noted. It is suggested that the "new" C.L. are responsible for the rebound of plasma progesterone reported in previous investigations three days following prostaglandin treatment in pregnant hamsters.