Lymphatic capillaries in rabbit ovaries during ovulation: an ultrastructural study

The fine distribution and ultrastructural changes of rabbit intraovarian lymphatics and blood vessels were compared in specimens obtained at accurately timed intervals after the injection of human chorionic gonadotropin (HCG). At four and six hours after HCG injection, edema was observed around blood capillaries with a slight increase in the number of small fenestrae in the theca interna. Edema around the lymphatic capillaries in the theca externa occurred a little later. The lymphatic capillaries were markedly dilated with occasional wide openings between adjacent cells. At this stage, lysosome disappeared in the endothelial cells of the lymphatic capillaries, and macrophages with numerous peculiar lysosomes appeared around the lymphatic capillaries and some of them entered into the lumen. By eight hours after HCG injection, the edema around the lymphatic capillaries had disappeared. The form and structure of the lymphatic capillaries resumed their pre-injection appearance, but the blood capillaries showed large gaps or perforations in the endothelium. At 11 and 18 hours after HCG injection, blood capillaries had penetrated into the membrana granulosa, but lymphatic capillaries had not. Thus, the lymphatics appear to be modified at four and six hours after HCG injection and these modifications are consistent with the removal of edematous fluid.