Progesterone secretion in the rat in response to an adjuvant arthritis challenge

This study was undertaken to determine if progesterone is secreted in response to an adjuvant-induced arthritis challenge in the rat. While the arthritic rat paw volume increased 33%, the plasma progesterone concentration increased from 502 pg/ml in the control rats to 1,202 pg/ml in the arthritic animals. A strong positive correlation was found between the degree of edema and the plasma progesterone concentrations. We suggest that progesterone may play an antiinflammatory role in adjuvant arthritis in the rat.