EPITHELIAL LOCALIZATION OF INSULIN-LIKE GROWTH-FACTOR BINDING-PROTEIN-1 IN THE UTERUS OF THE RAT DURING PREGNANCY, DECIDUOMA-BEARING PSEUDOPREGNANCY AND HORMONE-TREATMENT

A monospecific antibody was used to determine the immunocytochemical l ocalization of insulin-like growth factor binding protein 1 (IGFBP-1) in the rat utems. Immunoreactive IGFBP-1 was first detected from day 5 of pregnancy in the luminal and glandular epithelium. However, immuno reactivity was most intense from day 6 in the glandular epithelium, wh ere it was associated with apically located granules. Immunoreactive g lands were located only in non-decidualized endometrium, which was lim ited at the implant site to a thin basal layer by growth of the antime sometrial decidua from day 7. However, glands and associated immunorea ctive IGFBP-1 were prominent in the inter-implant sites until day 9, a lthough they were detected throughout pregnancy. Similar reactivity wa s detected in the glands of the basal endometrium in deciduomata-beari ng animals, but these decreased in number from day 7 of pseudopregnanc y. No immunoreactivity was detected during the oestrous cycle but coul d be induced in ovariectomized animals by sequential oestradiol and oe stradiol plus progesterone treatment. The observations were consistent with IGFBP-1 representing a secretory product of the glandular epithe lium and could either play a role in development of the trophoblastic component of the conceptus during the pre-placental period of anti-mes ometrial implantation or in the endometrium acting as an inhibitor of local IGF-I action and in either case by transporting IGF-I from the s tromal to the glandular luminal environment.