Fine structure and morphometric analysis of lymphatic capillaries in the developing corpus luteum of the rabbit.

The fine distribution and ultrastructural changes in the intraovarian lymphatics were studied in the developing corpus luteum of rabbits. Three days after human chorionic gonadotropin (HCG) injection, lymphatic capillaries were observed among theca lutein but not granulosa cells. This distribution persisted even on day 14. Edema appeared around the lymphatic capillaries, corresponding to dilatation of blood capillaries surrounding the membrana granulosa. The diameter and perimeter of the latter vessels were about 5 times greater than before HCG injection. Lymphatic capillaries were slightly dilated and about 2 times their original diameter and perimeter. Flocculent material migrated into the lumen of the lymphatics through the open junctions. Lysosomes and rough endoplasmic reticulum were increased in number in the lymphatic endothelial cells. Five and 7 days after HCG injection macrophages and sometimes loose, degenerated lutein cells were observed in the lymphatic capillaries. Fourteen days after HCG injection, the dilatation of blood capillaries disappeared, although lymphatic capillaries remained slightly dilated after day 3. Some lymphatic but not blood vascular endothelial cells began to degenerate. The results suggest that lymphatic capillaries function to absorb and transport excess fluid and "hormones" in association with changes in ultrastructure.