Enzyme-histochemical investigations on the lymphatics oe the intrinsic uterine wall in the monkey.

Topographic and ultrastructural characteristics in the monkey uterine lymphatics were demonstrated in the separate phases (proliferative, secretory and menstrual) of the sexual cycle and during pregnancy with 5’-nucleotidase (5’-Nase) and alkaline phosphatase (ALPase) staining methods. In the early proliferative phase, the newly forming and growing endometrial lymphatics with very irregular endothelial outlines were quite sparse and small in diameter (18-23 #1“), showing extremely weak 5’-Nase activity. The lymphatics in the secretory phase extended as far as the middle endometrium, and their endothelium obviously protruded into both the luminal and basal aspects. Abundant mitochondria and pinocytotic vesicles appeared in the cytoplasm. The most striking finding was that initial lymphatics in the middle endometrium are affected by sporadic episodes of cessation of blood supply, exhibiting a partial destruction of the endothelial wall during menstruation through which lymph fluid and numerous lymphocytes escape from the devitalized lymphatics into surrounding connective tissue. During pregnancy, lymphatic networks with high 5’-Nase activity in the endo-myometrial interface and myometrium were well developed and greatly enlarged, in contrast to those of the nulliparous monkey. Lymphatic endothelium with notable protrusions showed typical overlapping, interdigitating intercellular junctions and intraendothelial channels. The results indicated that uterine lymphatics are involved in the total processes of the sexual cycle, especially in the endometrium. Their continuous increment of the volumetric density and morphological changes during pregnancy may correspond to intensive growth of the fetus and prompt modification of the tissue metabolism, in cooperation with hemochorial relation between the mother and fetus. believed that the efferent lymph drainage may be Morphological studies ofthe uterine lymph drainage have predominantly been carried out by traditional injection techniques to demonstrate lymphatic gross contour and connexion between the ipsilateral ovary and uterus in the sheep (l, 14), rabbit (l7) and flying foxes (19). These studies had shown that the lymphatic plexus occurs limitedly at the endo-myometrial interface, but never extends into the endometrium. It has been Correspondence to: Dr R.C. Ji at the above address. Tel & Fax: +81-97-586-5623; E-mail: ][email protected]. in lacking in the endometrial layer in these mammalia (17, 22). In humans, however, a network of lymphatic capillaries was confirmed throughout the whole thickness of the endometrium by intratissue injection method (21). In rats, a few lymphatics were identified in the basal endometrium by using semithin sections stained with toluidine blue (5). These lymphatic capillaries were similar to those of the ovary, varying in size and shape cyclically in the ewe (3) and rabbit uterus after hCG injection (18). Thus, the distribution of initial lymphatics in