CYCLICAL EXPRESSION OF GNRH AND GNRH RECEPTOR MESSENGER-RNA IN LYMPHOID ORGANS

Gonadotropin-releasing hormone (GnRH) is known to possess dirct immuno modulatory effects, We have previously demonstrated that the administr ation of GnRH analogues modulates the expression of murine lupus indep endently of effects on gonadal steroids, We speculate that GnRH exerts direct actions at the level of the immune cells, GnRH receptors have been identified on lymphocytes, Because GnRH and GnRH receptor (GnRH-R ) expression varies with the estrous cycle at the levels of the hypoth alamus and pituitary, we speculated that similar cyclicity might be de monstrable in lymphoid tissue, In this report, we used competitive rev erse transcription PCR to quantitate the expression of GnRH and GnRH-R mRNA in lymphoid organs throughout the estrous cycle in mice. We demo nstrate that the pattern of expression of GnRH-R mRNA in spleen agrees closely with the pattern in the pituitaries of the same mice and the pattern previously reported in the rat pituitary, with significantly i ncreased levels of expression seen on the afternoon of proestrus compa red to the morning of metestrus, A similar pattern is seen with GnRH-R mRNA expression in the thymus, Furthermore, we show that the expressi on of GnRH mRNA in both thymus and spleen agrees closely with the patt ern of expression of its receptor, with significantly increased levels of expression seen on the afternoon of proestrus compared to the morn ing of metestrus, Additional in vitro studies demonstrate that both Gn RH and estradiol significantly increase the expression of GnRH-R mRNA in immune cells, These findings support an active role for GnRH in the immune system.