IMMUNOHISTOCHEMICAL STUDY OF ENDOMETRIAL MICROVASCULAR BASEMENT-MEMBRANE COMPONENTS IN WOMEN USING NORPLANT

The mechanisms responsible for progestogen-induced breakthrough bleedi ng remain unexplained, The aim of the present study sas to examine the expression of three basement membrane components, collagen IV (CIV), laminin and heparan sulphate proteoglycan (HSPG), by immunohistochemis try in sections of endometrium from women receiving the subdermal levo norgestrel implant (Norplant(R)) and normally cycling women, Control b iopsies were obtained from 20 normal subjects from Melbourne, Australi a, and pre- and post-Norplant-insertion biopsies were obtained from 11 women from Sydney, Australia, with between 3 and 6 months Norplant ex posure, It was postulated that. in Norplant users a decrease in the am ount of basement membrane material present around endometrial vessels may be responsible for increased capillary fi-agility. The results, ho wever, showed that: for all three components, Norplant biopsies exhibi ted vascular basement membrane immunostaining at least as intense as t hat found in the mid-late secretory phase of the normal cycle, During the normal cycle, HSPG was only detected in approximately 40% of vesse ls with CIV and laminin immunoreactivity, and menstrual biopsies demon strated reduced staining for all three components, Several biopsies ex hibited a degree of regional variability in staining intensity, and No rplant biopsies exhibited areas of discrete, decidual-like stromal imm unostaining for CIV and laminin, Although no differences were found in microvascular basement membranes in Norplant users that might explain capillary fragility, it is possible that other techniques could yield information on changes in the integrity of basement membrane componen ts that might influence basement membrane strength.