Hormonal Regulation of Immunoglobulins in the Rat Uterus: Uterine Response to Multiple Estradiol Treatments*

Abstract

The processes by which estradiol regulates the accumulation or IgA and IgG in the uterus were explored. Levels of IgG in uterine secretions increased rapidly within 3 h after either 2 or 3 daily estradiol (1 .mu.g) treatments of ovariectomized rats and then declined. These levels, however, were only a small fraction of the total IgG content measured in uterine tissue. In contrast, luminal IgA levels increased gradually, with maximal amounts occurring 6 to 25 h after the 3rd estrogen injection. Moreover, concentrations of IgA in uterine secretions at this time were significantly greater than those found in uterine tissue. Under the influence of estradiol, IgA moves from tissue to lumen against an apparent concentration gradient, while IgG movement is consistently down a gradient. Estradiol also rapidly increased the levels of IgA and IgG in uterine tissue. These increases, in contrast to the luminal pattern, occurred in parallel. Tissue content of both IgA and IgG were highest within 6 h after the 2nd or 3rd estradiol injection and then decreased. While the form of IgA in uterine tissue was both monomeric and polymeric, only polymeric IgA accumulated in the uterine lumen. Analysis of the effect of nafoxidine on the uterine Ig response indicated that this compound significantly increased the amount of uterine tissue IgA and IgG. The Ig levels in uterine secretions, however, were significantly less than those measured after estradiol treatment. Nafoxidine''s stimulatory effect on luminal Ig concentrations was equal to that of estradiol when uteri were ligated to prevent fluid loss through the cervix. Utilization of this ligation procedure was also instrumental in demonstrating that chronic estrogen exposure (8 days) resulted in greater quantities of uterine luminal Ig. The role of T cells in the estrogen control of uterine luminal Ig was also examined. In rats that had been neonatally thymectomized, luminal levels of both IgA and IgG were significantly reduced, when compared to those measured in sham-operated or intact estrogen-treated controls. Thymic absence, however, did not prevent the estradiol-induced movement of IgA from tissue to lumen against a concentration gradient.