Regulation of progesterone receptor isoforms expression by sex steroids in the rat lung

In this work, we determined the expression pattern and the hormonal regulation of progesterone receptor (PR) isoforms in the rat lung of ovariectomized female rats after estradiol (E2) and progesterone (P4) treatments. We also evaluated the content of estrogen receptor beta (ER-beta) which is the ER isoform expressed in the lung. RNA and proteins were extracted and processed for reverse transcription (RT) coupled to polymerase chain reaction (PCR) and Western blot, respectively. The expression of both PR isoforms in the lung at mRNA and at protein levels was up-regulated by E2 while P4 down-regulated it at mRNA level. P4 did not modify PR isoforms protein content unlike its effect in the uterus where both PR isoforms were down-regulated by their ligand at mRNA and protein levels. PR-A was the predominant isoform, both in the lung and in the uterus. In the lung, ER-beta was down-regulated by E2 while P4 did not significantly modify the effect of E2. These results suggest that both PR isoforms should be expressed in the rat lung, and that their expression should be differentially regulated at mRNA and at protein levels by P4. We also suggest that the up-regulation of PR isoforms by E2 in the lung is mediated by ER-beta. (C) 2003 Elsevier Science Ltd. All rights reserved.