Expression of Insulin-like Growth Factor-I in Uterus is Ovarian Steroid Dependent: An in situ Immunohistochemical Study in Rat

Abstract

Objective To study the immunohistochemical localization of insulin-like growth factor-I (IGF-I) in rats' uteri to determine if expression of the growth factor is ovarian steroid dependent. Method The study was carried out in presence and absence of ovary in situ of non pregnant females and during early gestation (day 1 to day 5.5). Cyclic females were tested to observe the effect of native steroids on IGF-I expression. Adult females were ovariectomized (OVX) and injected (s.c) with estradiol-17β in a dose of 0.1 μg/ml per day for three consecutive days at interval of 24 h prior to the collection of uterine horns. During the early pregnancy, studies were carried out on day 3.5 and day 5.5 of geatation respectively to determine the steroids' effects during pre- and post-implantation period. Tamoxifen was administered (s.c) in a dose of 250 μg/ml per day from day 1 to day 3 of gestation while, the prostaglandin F 2α (PGF 2α ) was administered (s.c) from day 3 of gestation onward for three consecutive days at interval of 24 h in a dose of 150 μg/ml per day. Expression of IGF-I was immunohistochemically localised using IGF-I antibody in paraffin embedded sections. Results IGF-I was expressed in rat uterus during estrus phase as well as during pre and post-implantation period. The ovariectomized females' uteri lost the expression of IGF-I. Exogenous administration of tamoxifen and PGF 2α reduce the expression of the growth factor. Conclusion Expression of IGF-I in rat uterus during cyclic stage and early gestation depends upon the availability of circulating estrogen and progesterone. Uterine expression of IGF-I can be modulated by manipulating circulating ovarian steroid either during cyclic stage or during gestation.