Progesterone modulation of anaphylactically induced ion transport in uterus and intestine

The objective of this study was to investigate the role of progesterone in modulating electrophysiological responses to antigenic challenge that are reflective of immune functions in uterine and jejunal mucosae. In the rat-Trichinella spiralis, host-parasite system, an enteric infection with a microscopic nematode sensitizes both the jejunum and uterus. Electrophysiological correlates of local anaphylaxis or type I hypersensitivity were monitored in vitro throughout the estrus cycle and during pregnancy. The magnitude of the anaphylactic response was correlated with serum levels of progesterone. Functional immunity was measured directly in the intestine by assessing the development of acquired resistance to reinfection with T. spiralis. Results support the conclusion that high progesterone output, as occurs during metestrus and pregnancy, and exogenously administered hormone suppress uterine responsiveness. However, the reduced uterine sensitivity to challenge could be attributed to nonspecific physiological effects of progesterone rather than direct effects on immunological components involved in the transduction of the antigenic signal. The electrophysiological response to antigen in the intestine was relatively refractory to effects of progesterone. These observations add to our understanding of endocrine control of mucosal responses to antigenic challenge and underscore site selectively of hormonal action.