ENOS, ET-1 and ETB-R immunoreactivities in the porcine mesometrial lymphatics during the estrous cycle.

Abstract: Immunohistochemical localization and distribution of nitric oxide synthase (eNOS), endothelin (ET-1) and endothelin beta receptor (ETB-R) were investigated in precollector and collector lymph vessels in the broad ligament of the uterus during different phases of the estrous cycle in pigs. The polyclonal antibody for ET-1 and ETB-R and monoclonal antibody for eNOS isoform were used to perform observations on the light microscopic level. Immunoreactivities to ET-1, ETB-R and eNOS were observed in the endothelium of precollector and collector lymphangions but not in smooth muscle cells of the lymphatics examined. The staining for eNOS in the endothelial cells of all studied lymphatic vessels was stronger comparing to ET-1 and ETB-R. During the estrous cycle, only eNOS showed the correlation with the particular phases of the estrous cycle. The differences between ET-1 and ETB-R immunoreactivities were very slight and rather independent of the size or type of the lymphatic lymphangions and estrous cycle. The highest immunoreactivity level for eNOS was displayed by collector lymphangions with widened lumen in the follicular phase comparing to the precollector ones. During the luteal phase, a slight decrease in the reaction intensity was observed. The immunoreactivities for ET-1 in the endothelium of the studied vessels was not comparable with the presence or with the reactivity level of ETB-R. Optically stronger immunoreaction for ETB-R was observed in the cytoplasm of collector lymphangions in the follicular phase. eNOS, ET-1 and ETB-R were also present in the cytoplasm of the lymphatic valves. These results suggest that ET-1 and eNOS can play a role in the mechanisms regulating the vascular contractile activity, promoting lymph flow during the estrous cycle in the porcine broad ligament.