EXPRESSION OF THE CHICKEN PROGESTERONE-RECEPTOR FORM-A AND FORM-B IS DIFFERENTIALLY REGULATED BY ESTROGEN IN-VIVO

The chicken progesterone receptor (cPR), like its human counterpart (h PR), exists as two isoforms, PRA and PR-B, displaying different biolog ical activities depending upon cellular and promoter contexts, Here we show that the ratio of PR isoforms observed in the immature chicken o viduct is changed during estrogen-induced differentiation from PR-B do minancy to that of PR-A. This is the first report describing that the expression ratio of PR isoforms is altered by upregulation of PR-A by estrogen action in vivo. This result provides a plausible explanation to the differences in oviduct's response to progesterone depending on hormonal and developmental status of the animal. (C) 1997 Academic Pre ss.